Big Huge Chem Mid Term Study Guide
molality (m)
moles of solute/kg of solvent mol/kg
molarity (M)
moles of solute/liters of solution mol/L
Examine this chemical reaction and answer the question that follows: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy In this combustion of sugar, is ΔH positive or negative?
negative
Is the entropy, △S, positive or negative for the following process? Assembling a jigsaw puzzle.
negative
Is the entropy, △S, positive or negative for the following process? Constructing a miniature log house from Legos® building logs
negative
A heat flow can never be from the surroundings to the system.
no
When the change in temperature, ΔT, is negative, the phase change is endothermic.
no
entropy of a liquid is higher than a solid, and a gas is higher than a liquid
true
Calculate the freezing point of a 2.00 molal solution of magnesium perchlorate, Mg(ClO4)2, in water.
-11.16 C
Calculate the freezing point of a solution made from 94.0 grams of sucrose, C12H22O11, dissolved in 300 grams of ethanol.
-116.42
Convert 245 K to C
-28 C
Convert 235 K to C
-38 C
Convert 228 K to C
-45 C
Using the data in the table below, solve the following problem. Calculate the freezing point of a 1.40 molal solution of nickel(II) sulfate dissolved in water.
-5.21 C
Kinetic molecular theory 5 assumptions
-gases consist of a ton of spherical particles that are far apart relative to their size -particles are in constant and rapid and random motion -any collisions are considered elastic collisions -no forces of attraction/repulsion between particles -average kinetic energy depends on temp
Absolute Zero is defined as
0 K
What is absolute zero?
0 Kelvin -273 degrees celsius
What is the molarity of a solution in which 5.75 grams of AgNO3 are dissolved in 250. mL of solution?
0.135 M
What is the molality of a solution in which 14.5 grams of NaCl is dissolved in 1.50 kilograms of water?
0.165 m
Aluminum reacts with sulfur to form aluminum sulfide according to the following reaction: 2 Al (s) + 3 S (s) → Al2S3 (s) How many moles of sulfur will be needed to react with 5.00 grams of aluminum?
0.278 mol S
Convert 725 mm Hg pressure to atm
0.95 atm
If 12.5 grams of calcium is reacted with excess hydrogen chloride in a water solution according to the following chemical reaction, and the measured amount of 23.5 grams of calcium chloride is produced, what is the percent yield for the reaction? Use the balanced equation given below. Ca (s) + 2HCl (aq) → CaCl2 (aq) + H2 (g) First, calculate the theoretical yield, then calculate the percent yield. You must show all your work with calculations with a proper set up including: how you find the molar mass of CaCl2? how you calculate the theoretical yield? how you calculate the correct percent yield?
1) To find the molar mass of CaCl2, I'll add the masses of Ca and Cl2 together. 40.08 + 70.90 = 110.98 g/mol 2) To calculate the theoretical yeild, I first need to find the moles of CaCl2 produced. I can do this using the train tracks method: 12.5 g Ca x 1 mol Ca / 40.08 g/mol Ca = 0.31 mol Ca Now I can use this to find the theoretical yeild by first finding how many mols of CaCl2 produced and then how many grams. 0.31 mol Ca x 1 mol CaCl2/1 mol Ca = 0.31 mol CaCl2 Now I'll convert it to grams. 0.31 mol CaCl2 x 110.98 g / 1 mol CaCl2 = 34.40 grams CaCl2 produced 3) finally, I'll divide the actual yield by the theoretical yield to find my percent yield. 23.5 g CaCl2/34.40 g CaCl2 = 0.68 x 100% = 68%
Sodium chloride reacts with silver nitrate in a water solution, producing aqueous sodium nitrate and solid silver chloride. 1) Write a balanced chemical equation for the reaction. Include the phases for all reactants and products. 2) What mass of sodium chloride is needed if 3.00 moles of silver nitrate are reacted? Show all of your work. To receive full credit, show all of your work, including ratios and molar mass calculations.
1. NaCl (aq) + AgNO3 (aq) -> NaNO3 (aq) + AgCl (s) Using a periodic table, I found the charges of each element or compound and made sure they were properly balanced. 2. We only have 1 mole of every compound in the equation above, and I know there are 3.00 mol of silver nitrate. Now I'll set up my equation. 3.00 mol AgNO3 x (1 mol NaCl/1 mol AgNO3) x (22.99 g/mol Na + 35.45 g/mol Cl)/(1 mol NaCl) = 175.32 grams Final answer for part 2: 175 grams of NaCl are needed.
Convert 825 mm Hg to atm
1.09 atm
What is the molality of a solution in which 125 grams of NaNO3 is dissolved in 750.0 grams of water?
1.96 m
Calculate the boiling point of a 1.40 molal solution of nickel(II), NiSO4, sulfate dissolved in water.
101.43 C
Calculate the boiling point of a 2.00 molal solution of magnesium perchlorate, Mg(ClO4)2, in water.
103.72 C
A gas volume, 135 mL, is measured at 52 C. What is the gas volume at -12 C of the pressure does not change?
108 mL
A gas volume, 135 mL, is measured at 52oC. What is the gas volume at -12oC of the pressure does not change?
108 mL
Aluminum reacts with sulfur to form aluminum sulfide according to the following reaction: 2 Al (s) + 3 S (s) → Al2S3 (s) How many grams of aluminum sulfide will be produced if 5.00 grams of aluminum is reacted with excess sulfur?
13.9 g Al2S3
A sample of argon gas at 55 C is under 845 mm Hg pressure. What will the new temperature be if the pressure is raised to 1050 mm Hg?
135 C
What is the mass percent of a solution in which 25.0 grams of NH4Cl is dissolved in 125.0 grams of water?
16.7%
Aluminum reacts with sulfur to form aluminum sulfide according to the following reaction: 2 Al (s) + 3 S (s) → Al2S3 (s) How many moles of sulfur will be need to produce 6 moles of aluminum sulfide?
18 mol S
In a chemical reaction between nitrogen and hydrogen, 5.0 moles of hydrogen react with excess nitrogen. To determine how many moles of ammonia are produced, what conversion factor should be used? Use this balanced equation for the Haber process: N2 (g) + 3 H2 (g) → 2 NH3
2 mol NH3/3 mol H2
What is the molarity of a solution in which 175 grams of KCl are dissolved in 1.00 L of solution?
2.35 M
A chemical reaction is conducted in a calorimeter, and the temperature of 100.0 mL of water rises from 21.5oC to 75.0oC. How much heat was transferred in the reaction?
22,400 joules ΔT = Tf - Ti = 75.0 C - 21.5 C = 53.5 C q = m c ΔT = (100.0 g)(4.18 J/g C)(53.5 C) = 22400 joules
The standard state is defined as _____________.
25 C and 1 atm
mass percent ex
25 g sugar into 100g water 25 g/125 g = 0.2 x 100% = 20% sugar
molality ex
28.60 g of glucose (C6H12O6) in 250 g water -molar mass: 180.18 g/mol C6H12O6 28.6 g x 1 mol/180.18 g = 0.1587 mol 0.1587 mol/0.250 kg = 0.635 m
Convert 19 C to K
292 K
When potassium chlorate is heated, it decomposes into potassium chloride and oxygen gas according to the following chemical equation: 2 KClO3 (s) → 2 KCl (s) + 3O2 (g) If you start with 0.75 moles of potassium chlorate, what mol-mol ratio would you use to determine how many moles of oxygen are produced?
3 mol O2/ 2 mol KClO3
How many moles of ammonia are produced when 5.0 moles of hydrogen react with excess nitrogen? Use this balanced equation for the Haber process: N2 (g) + 3 H2 (g) → 2 NH3
3.33 mol NH3
What is the volume percent of a solution in which 35.0 mL of isopropyl alcohol is dissolved in water to make a 1.00 liter solution?
3.50%
If 2.75 grams of calcium react with 1.10 grams of oxygen in the following reaction, what mass of calcium oxide will be produced? 2 Ca (s) + O2 (g) → 2 CaO (s)
3.85 g CaO
Convert 28 C to K
301 K
What mass of iodine is required to react with 5.65 grams of sodium to produce 36.85g of sodium iodide according to the following reaction: 2Na (s) + I2 (s) → 2 NaI (s)
31.20 g I2
A sample of gas at a pressure of 0.850 atm has a volume of 675 mL. What will the volume be if the pressure is increased to 1.50 atm?
383 mL
Convert 312 K to degrees C
39 C
37.5 mL of oxygen gas is collected at a pressure of 772 mm Hg. What is its volume at 716 mm Hg?
40.4 mL
freezing point depression example
400 g of C2H6O2 in 500 g of H20 400 g C2H6O2 x 1 mol/62.08g = 6.44 mol C2H6O2 6.44 mol/0.5 kg H20=12.9 m c2H6O2 ∆Tf= -1.86 C/m x 12.9 m C2H6O2 ∆Tf= -24.0 C So, added substance made the freezing point 24 degrees lower.
molarity ex
42.23 g NH4Cl into enoguh water for 500 mL -molar mass of NH4Cl: 53.50 g/mol 42.23 g NH4Cl x 1 mol/53.50 = 0.7893 mol NH4Cl Now, we do 0.7893 mol NH4Cl/0.5000 L = 1.579 M
Convert 0.566 atm to mm Hg
430 mm Hg
Ethane gas (C2 H6) burns to produce carbon dioxide and water according to the following chemical equation. All gases are measured at the same temperature and pressure: 2 C2 H6 (g) + 7 O2 (g) → 4 CO2 (g) + 6 H2O (g) How many liters of carbon dioxide are produced from 2.50 liters of ethane?
5.00 L CO2
Convert 0.853 atm to mm Hg
648 mm Hg
Pressure conversion example
725 mm Hg/1 x 1 atm/760 mm Hg = 0.954 atm
Examine the table of Molar Heats of Fusion and Vaporization below and answer the question that follows. What is ΔH when 755 grams of ethanol (C2H5OH) is melted (at its freezing point)?
75.4 kJ
Convert 352 K to C
79 C
Ethane gas (C2 H6) burns to produce carbon dioxide and water according to the following chemical equation. All gases are measured at the same temperature and pressure: 2 C2 H6 (g) + 7 O2 (g) → 4 CO2 (g) + 6 H2O (g) How many liters of oxygen are required to react with 2.50 liters of ethane?
8.75 L O2
Convert 1.08 atm to mm Hg
821 mm Hg
endothermic reaction
A reaction that ABSORBS energy in the form of heat
exothermic reaction
A reaction that RELEASES energy in the form of heat
formation reaction
A reaction that starts with two or more elements and produces one compound
In the lab, a 149 gram sample of a metal, which had been heated to 47.55oC, was placed in a calorimeter containing 50.0 mL of water at 22.00 oC. Once the system reached equilibrium, the final temperature was 27.50 oC. Answer these questions: A. What was the specific heat of the metal? Show all of your work for full credit. B. Which metal is it?
A. First I have to change up my equation to equal the specific heat (c). I'll do this by dividing both sides by (m x At) and I'll get q/mAt=c. Since I don't know the (q) value, I have to first solve for that by finding the heat in J. I'll put that into my regular equation. q=mcAt q= (50 g H2O) x (4.18 J/g C) x (27.50 degrees C - 22.00 degrees C) q= 1149.5 J Now that we know J, we can enter it into our other equation. c= (1149.5 J) / (149 g) x (47.55 degrees C- 27.50 degrees C) c= 1149/2987.5 c= 0.385 J/g C is the specific heat of the metal B. From the chem info sheet, I know that this metal is Copper!
According to the collision theory, ________________.
As the concentration of the reactants increases, the rate of reaction increases.
ex of formation reaction
Ba (s) + Cl2 (g) = BaCl2 Yes! Equation is balanced and only 1 mol produced 2Ca (s) + O2 (g) = 2CaO No! 2 mols were produced!
entropy ex
CaCO3 (s) -> CaO (s) + CO2 (g) increase; gas is produced and # of molecules increases
entropy ex
Cl2 (g) -> Cl2 (l) decrease; gas becomes liquid
As the sun warms the surface water on a lake, _____________ a) convection will cause the warmer water will remain on the top b) convection will cause the the warmer water to sink to the bottom c) conduction will cause the the warmer water to sink to the bottom d) the warmer water will remain on the top, if there are no disturbances to the water e) none of the above
D
Gay-Lussac's Law
P1/T1=P2/T2 Direct relationship Ex: a gas in under 3.00 atm at 25 C. What is pressure at 845 C? P2= P1 x T2 / T1 P2= 11.3 atm
Gases can conduct heat easily because the particles have high kinetic energy.
False
If two gas particles collide, they may both lose kinetic energy.
False
Metal is used for cooking pots and pans because metal does not easily transfer heat from the burner to the food.
False
Snow must melt before it changes into the vapor phase.
False
What do we use mole ratios for?
Finding the unknown amount of a substance in moles.
When chloroform changes phase from a liquid to a gas, △H = 29.2kJ/mol, and △S = +75.7J/Kmol. Calculate the free energy, △G, for this reaction when the temperature is 125oC. Is the reaction spontaneous?
First I have to convert 125 degrees C to Kelvin, which I can do by adding 273, and I'll get 398 K. I also have to convert my ΔS from J/Kmol to KJ/kmol, which I can do by dividing it by 1000 to get 0.0757 KJ/kmol. Now I can input it into my equation and solve. ΔG= ΔH-TΔS ΔG= 29.2 kJ/mol - (398 K x 0.076 KJ/kmol) ΔG= 29.2 - 30.2 ΔG= -1.00 kJ/mol This reaction is spontaneous.
The chemical equation for producing hydrogen from the reaction between water and carbon is as follows: C (s) + H2O (l) → CO (g) + H2 (g). For this reaction, △H = 131 kJ/mol, and △S = 134J/Kmol. Calculate the free energy, △G, for this reaction when the temperature is 305K. Is the reaction spontaneous?
First I have to convert the ΔS from J/Kmol to KJ/kmol which I can do by dividing my 134 by 1000, and I'll get 0.134 KJ/kmol. Now I can input everything into my Gibbs free energy equation. ΔG= ΔH-TΔS ΔG= (131 kJ/mol) - (305 K x 0.134 KJ/mol) ΔG= 131 - 40.87 ΔG= 90.13 KJ/mol The reaction is not spontaneous.
In a chemical reaction shown in the equation below, ammonia reacts with nitrogen monoxide to produce nitrogen and water. 4 NH3 + 6 NO → 5 N2 + 6 H2O This reaction produced 14.80 mol water. How many moles of NO reacted?
First I have to put the factors into my mole ratio, and I get: 14.80 mol H2O x (6 mol NO/6 H2O). Now, I can simplify this expression and get my final answer. 14.80 mol NO reacted to produce 14.80 mol H2O.
In a chemical reaction shown in the equation below, ammonia reacts with nitrogen monoxide to produce nitrogen and water. 4 NH3 + 6 NO → 5 N2 + 6 H2O This reaction produced 14.80 mol water. How many moles of NH3 reacted?
First I have to set up my mole ratio. 14.80 mol H2O x (4 mol NH3/6 mol H2O) I remembered to put the unknown value into the numerator and the known value in the denominator. Now I can simplify and get my final answer. 9.866 mol of NH3 are needed to produce 14.80 mol H2O.
In a chemical reaction shown in the equation below, ammonia reacts with nitrogen monoxide to produce nitrogen and water. 4 NH3 + 6 NO → 5 N2 + 6 H2O. How many moles of NO are required to completely react with 2.45 mol NH3? Show all of your work as well as the answer with the proper units.
First I have to set up my mole ratio: 2.45 mol NH3 x (6 mol NO/4 NH3) I put the known amount on the bottom and the unknown amount on top. Now I can simplify to get my answer. 3.68 mol NO are required to react with 2.45 mol NH3.
In a chemical reaction shown in the equation below, ammonia reacts with nitrogen monoxide to produce nitrogen and water. 4 NH3 + 6 NO → 5 N2 + 6 H2O How many moles of NH3 are necessary to produce 0.824 mol N2?
First I'll set up my mole ratio: 0.824 mol N2 x (4 mol NH3/5 mol N2) Now that I put my known as the denominator and the unknown as the numerator, I can simplify and get my final answer. 0.659 mol of NH3 are required to produce 0.824 mol N2.
Determine the heat of reaction of the following chemical reaction using the standard heats of formation from the table in the Chemistry B Information Sheet. Show all of your work. Then classify each reaction as endothermic or exothermic. C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (l)
First ill list my knowns. ΔHf° of C2H5OH (l): -276.98 kJ/mol ΔHf° of 3 O2 (g): 0 (pure element) ΔHf° of 2 CO2 (g): -393.5 kJ/mol ΔHf° of 3 H2O (l): -285.5 kJ/mol Now I can insert those values into my equation and solve. ΔH= [2 mol CO2 (g) (-393.5 kJ/mol) + 3 H2O (l) (-285.8 kJ/mol)] - [1 mol C2H5OH (l) (-276.98 kJ/mol) + 3 mol O2 (g) (0 kJ/mol)] ΔH= −1644.4 - (-276.98) ΔH= -1367.4 kJ This reaction is exothermic.
Magnesium metal reacts with a solution of silver nitrate in a single-replacement reaction, producing aqueous magnesium nitrate and silver metal. If a reaction starts with 0.480 mol Mg, how many moles of silver are produced? You must show a proper set up for the calculation, the answer with a proper unit, and the proper significant figures.
First, I had to set up a balanced equation of the reaction. Mg (s) + 2AgNO3 (l) -> Mg(NO3)2 (aq) + 2Ag (s) Now I can set up my mole ratio. 0.480 Mg x (2 mol Ag/1 mol Mg) Now I simplify the expression to get my final answer. 0.960 mol Ag are produced with 0.480 mol of Mg.
Calculate the density of a 7.0% solution of sodium chloride in water if it has a volume of 40.0 mL and a mass of 42.08 grams. (1 point)
For this, I have to use my formula D=m/v. I can fill it in now with my values. D= 42.08 g/40.0 mL D=1.052 g/mL
Hvap and Hcond are opposites
Hvap will be pos and Hcond will be neg
Use the table of Specific Heat below to answer the question. Show all of your work for full credit: Calculate the number of joules required to raise the temperature of 45.0 grams of lead from 21.5oC to 57.2oC.
I know I have to use the q=mcAt equation and plug all my values into it. Everything is already in the right units and I don't have to change the equation because I'm solving for q. (Also, I'm using the letter A to symbolize the delta symbol because I don't know how to get the delta in the text box. I'm doing this for all my problems). q= (45 g Pb) x (0.129) x (57.2 degrees C - 21.5 degrees C) Now I simplify. q= 207.2 J
Magnesium metal reacts with a solution of silver nitrate in a single-replacement reaction, producing aqueous magnesium nitrate and silver metal. Write the balanced equation for the reaction.
I listed all the products and reactants by looking at a periodic table and the information sheet. Then, I looked at the problem and found their states in the words. Last, I had to balance the equation. Mg (s) + 2AgNO3 (l) -> Mg(NO3)2 (aq) + 2Ag (s)
Sugar Water Density vs Pure Water Density Lab We learned that aqueous solutions have higher densities than pure water in the lesson.Because of the density differences of the sugar water solutions (which have different concentrations), we can create a rainbow-colored water tower just like the one we saw in the YouTube video "Easy Water Stacking Sugar Density Experiment" Let's consider a new experiment. This time, prepare four solutions containing different colors of food color in water, but without sugar. If we carefully poured each solution, one at a time, into a tall glass, what do you think would happen? Explain why you think this would happen in terms of the densities of the solutions.
I think the mixtures would probably mix together instead of layering like they did in the video. This is because there is nothing to change the density; in the video, the concentration of sugar changed the density so that the blue had a greater density and the red had the lowest density. Without this change in concentration of sugar, I think the colors would just mix instead of layering.
Using this solubility curve, answer the following question. Which of the following solids is least soluble at 10°C?
KClO3
Use the table of Specific Heat below to answer the question. Show all of your work for full credit: Calculate the number of joules given off when 35.0 grams of water is cooled from 45.5°{"version":"1.1","math":"<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>°</mo></math>"}C to 22.5°{"version":"1.1","math":"<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>°</mo></math>"}C.
Ok so I have to use the q=mcAt equation like last time, just plug in my values from this equation. q=mcAt q= (35 g H2O) (4.18) (22.5 degrees C - 45.5 degrees C) Now I can simplify. q = -3364 J
Which will be stronger? a) N - H b) N = O
N = O
Which will be stronger? a) N ≡ N b) N = O
N ≡ N
entropy ex
N2 (g) + 3H2 (g) -> 2NH3 (g) decrease; 4 reactant moles form 2 product moles
The heat value, q, for an endothermic reaction is negative.
No
Combined gas law
P1V1/T1=P2V2/T2 Ex: 2L gas at 35 C (308 K) and 0.833 atm is brought to STP (273 K). New volume? V2=P1 x V1 x T2 / P2 x T1 V2= 0.833 c 2 x 273/ 1 x 308
Boyle's Law
P1V1=P2V2 inverse relationship Ex: O2 is placed in a 425 mL container, and the pressure is 387 kPa. The gas is then put in a 1.75 L container. Calculate new pressure. P2=P1 x V1 / V2 P2= 387 kPa x 425 mL / 1750 mL P2= 94.0 kPa
Ideal gas law
PV = nRT P = pressure in atmospheres V = volume in liters n = number of moles R = gas constant (0.0821 L atm/mol K) T = temperature in Kelvin Rearrange as needed.
Iron oxide is reacted with hydrogen gas to produce elemental iron and steam in the following reaction: Fe2O3 (s) + 3 H2 (g) → 2 Fe (s) + 3 H2O (g) What mass of iron will be produced from 875 grams of iron oxide? Show all of your work. (5 points)
Set up my equation: 875 g Fe2O3 x 1 mol Fe2O3/ ((55.85 g/mol Fe x 2)+(16.00 g/mol O x 3)) x 2 mol Fe/1 mol Fe2O3 x (2 x 55.85 g/mol Fe) Final answer: 1224 g Fe
Use the table of Specific Heat below to answer the question. Show all of your work for full credit: If it requires 2274 joules of energy to warm a 85.0- gram block of wood from 21.5 C to 36.7 C, what is the specific heat of wood?
Since I have to solve for c, I have to rearrange the problem to equal c. I do this by dividing both sides of the equation by (m times change in t) and I get q/mAt=c. Now I can plug in my values. c=q/mAt c = 2274 J / (85.0 g wood) (36.7 degrees C - 21.5 degrees C) Now I simplify for c. c = 1.760 J/(kgC) is the specific heat for wood
In the lab, a sample of a hot metal is placed in a calorimeter that contains 50.0 grams of water at 21.0oC. The temperature of the water rises to 33.5oC. Calculate the heat (in joules) lost by the metal when it cooled. Show all of your work for full credit.
So I know I have to use the formula q=mcAt (I'm using A to symbolize the delta). I'll fill in my givens. q=(50 g H2O) x (4.18 J/g C) x (33.5 degrees C - 21.0 degrees C) q=(50 g H2O) x (4.18 J/g C) x (12.5 degrees C) q= 2612.5 J The metal lost 2612.5 Joules of heat when it cooled.
A gas cylinder with a volume of 15.0 liters contains 1.75 moles of nitrogen gas at 17.5oC. What is the pressure inside the cylinder? Show all of your work for the following problems, including unit conversions, for full credit. Pay attention to the significant digits and the units.
So I started out by switching up the Ideal Gas Law Equation. Since I need to get pressure alone on one side, I divided both sides by volume and got an equation of P=nRT/V. I see that the temperature is in Celsius, so I need to add 273 to the 17.5 to get a temperature of 290.5 Kelvin. Now I plug in my givens. P=(1.75 mol N)(0.0821 L*atm/mol*K)(290.50 K)/(15.0 L) P= 2.78 atm
A 1.25 mol sample of nitrogen gas is in a 10.0 liter cylinder at 2.15 atmosphere of pressure. What is the temperature of the gas? Problems: Show all of your work for the following problems, including unit conversions, for full credit. Pay attention to the significant digits and the units.
So for this one I have to change the equation up again to get T alone, which I can do by dividing both sides by nR. I get PV/nR=T. I don't have to do any conversions, so I can just plug everything in and get my answer. T=PV/nR T=(2.15 atm)(10 L)/(1.25 mol)(0.0821 L*atm/mol*K) T= 209 K
Examine this photosynthesis reaction and answer the question that follows: 6 CO2 + 6 H2O + Energy → C6H12O6 + 6 O2 Which is larger, a) the energy needed to break the bonds in CO2 and H2O, or b) the energy given off when new bonds in C6H12O6 and O2 are formed?
The energy needed to break the bonds in CO2 and H2O is larger.
Consider the reaction H2 (g) + Br2 (l) → 2 HBr (g). Which would you predict to be spontaneous based only on △S, the first reaction given or the reverse reaction?
The first reaction is more likely to be spontaneous.
A 345 mL sample of gas is in a container at 18oC and 3.50 atmospheres of pressure. How many moles of gas are in the sample? Show all of your work for the following problems, including unit conversions, for full credit. Pay attention to the significant digits and the units.
To find moles in the sample, I need to change up the equation to equal n. To do this, I will divide both sides by RT to get an equation of PV/RT=n. Now I have to convert 18 degrees C to Kelvin, which I will do by adding 18 to 273 to get 291 K. Now I have to convert the mL of gas to L, which I'll do by dividing it by 1000. I'll get 0.345 L. Now I can plug everything into my equation and solve. n=PV/RT n= (3.50 atm)(0.345 L)/(0.0821 L*atm/mol*K)(291 K) n= 0.05 moles of gas in the sample
An aqueous 20% BaCl2 solution has a mass of 90.23 grams and a volume of 75.0 mL. What is the density of the solution? (1 point)
To find the density I can fill in my density equation D=m/v D=90.23 g/75.0 mL D= 1.203 g/mL
All particles in a gas sample have the same average kinetic energy at the same Kelvin Temperature.
True
Conduction transfers thermal energy between particles of matter that are touching.
True
Frozen meat will thaw more quickly when placed in water rather than air, because water conducts heat better than air.
True
Gas molecules travel independently and in constant random motion.
True
Most of the volume in a sample of gas at 25oC and 1 atm is empty space.
True
The kinetic energy of a gas particle can be transferred to another gas particle or to the wall of the container in a collision.
True
The vapor pressure of a liquid depends on its temperature.
True
To calculate the unknown quantities of substances involved in a chemical reaction, we use stoichiometry.
True
Charles' Law
V1/T1=V2/T2 Direct relationship Ex: a balloon has 2.20 L at 22 C (295 K). It is heated to 71 C (344 K). Find new volume. V2=V1 x T2 / T1 V2-= 2.2 L x 344 K/295 K V2= 2.57 L
When you put food in the freezer, the heat flows from the food to the air in the freezer.
Yes
calorimetry ex
a hot metal is put in a 75g calorimeter of water at 22.25 C. the temp rises to 53.75 C. calculate heat lost by metal. q=mcAt q=75 g x 4.18 J/g C x 31.50 C q=9880 J
Conduction will occur the easiest in ___________.
a solid with high density
Which gas would act most like an ideal gas? a) xenon at 1.1 atmosphere of pressure b) xenon gas at 9.25 atmospheres of pressure
a) 1.1 atm Xenon gas at 1 atmosphere of pressure would act more like an ideal gas. At the higher pressure, the volume of the gas particles is more significant, and one of the assumptions of the kinetic-molecular theory states that the volumes of the gas particles themselves are insignificant.
Which gas would act most like an ideal gas? a) argon, Ar b) chlorine, Cl2
a) ARGON!
Using this solubility curve, answer the following question. How many grams of KNO3 are required to make a saturated solution in 100 g of water at 50°C?
about 85 g
Using this solubility curve, answer the following question. At what temperature is a solution of 55 grams of KCl dissolved in 100 grams of water a saturated solution?
about 90 C
covalent compound
all nonmetals and breaks apart in smaller compounds
ionic compound
breaks apart into individual atoms
Given 115 mL of oxygen gas measured at 17oC and 485 mm Hg, what volume in milliliters will the gas occupy at 107oC and 605 mm Hg? Question options: a) 188 mL b) 121 mL c) 1950 mL d) 580 mL e) 70.4 mL
b) 121 mL
Which gas would act most like an ideal gas? a) chlorine gas at -185 C b) chlorine gas at 32 C
b) 32 C Chlorine gas at 32 C would act more like an ideal gas. At the lower temperature, the gas particles move more slowly and are more subject to attracting each other because of intermolecular forces. The kinetic-molecular theory assumes that there are no intermolecular forces.
Which gas would act most like an ideal gas? a) carbon monoxide, CO b) oxygen, O2
b) OXYGEN!
Examine this chemical reaction and answer the question that follows: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy Which is larger, a) the energy needed to break the bonds in C6H12O6 or b) the energy given off when new bonds in CO2 and H2O are formed? a) The energy needed to break the bonds in C6H12O6 and O2 is larger. b) The energy given off when new bonds in CO2 and H2O are formed is larger.
b) The energy given off when new bonds in CO2 and H2O are formed is larger.
The specific heat of a substance depends on _________. a) the mass of the substance b) the initial temperature of the substance c) the final temperature of the substance d) all of the above e) none of the above
e) none of the above
Hess's law example
calculate ∆H ^o for NO gas with oxygen to form NO2. NO (g)= 90.4 kJ/mol O2 (g)= 0 (pure element) NO2= 33.85 kJ/mol 2 mol NO2 (33.85) - 2 mol NO2 (90.4) + 1 mol O2 (0) = -113 kJ
Factors that influence reaction rates
concentration (increase, increase speed) pressure (increase, increase speed) surface area (increase, decrease speed) temp (increase, increase speed) catalyst (depends!)
The change from gas to liquid is called ________.
condensation
gas to liquid
condensation
Glue melting in a glue gun is an example of the transfer of thermal energy by ____________.
conduction
Solids can transfer heat by ____________.
conduction
Waffle batter cooking in a waffle iron is an example of the transfer of thermal energy by _________________.
conduction
Which of the following requires particles that are close together to transfer thermal energy?
conduction
Cool air blowing onshore from the ocean at night is an example of __________.
convection
Gases can transfer heat by _____________.
convection
liquid to solid
freezing
Liquids can transfer heat by _____________. Question options: a) conduction b) convection c) radiation d) both a and b e) both b and c
d) both a and b
What do the coefficients of substances in a balanced equation represent? Question options: a) moles b) molecules (or formula units) c) mass d) both a and b
d) both a and b
The solubility of a substance _______________________________________________.
depends on the temp
gas to solid
deposition
Heat of reaction ___________. Question options: a) can be indicated in the balanced chemical equation b) is always found on the reactant side of the chemical equation c) is the same as the enthalpy change for a reaction d) all of the above e) a and c
e) a and c
Which of the following assumptions are true for the kinetic-molecular theory? Question options: a) Gas particles are in constant rapid motion in random directions. b) Collisions between gas particles and between particles and the container walls are elastic collisions. c) The motion of each particle is completely independent of the motion of all other particles. d) The average kinetic energy of gas particles is not dependent upon the temperature of the gas. e) a, b, and c are correct
e) a, b, and c are correct
In calorimetry, _________________. Question options: a) the calorimetry container is insulated b) there is no heat exchange between the calorimeter and the room c) only increases in temperature can be measured d) the water is the "surroundings" for the reaction e) a, b, and d
e) a, b, and d
Which of the following is true about enthalpy? Question options: a) Enthalpy change is the same as the heat absorbed or released in a chemical reaction b) Enthalpy is measured at a constant pressure c) Enthalpy is represented by ΔH. d) Enthalpy can be measured in a calorimeter in the lab. e) All of the above.
e) all of the above
Solutions _________________________________________. Question options: a) are always composed of a solid dissolved in a liquid b) can be composed of two substances in any phases c) have a definite concentration d) have a concentration that depends on the amount of solute e) b & d
e) b & d
As the temperature of a gas decreases Question options: a) the motion of the particles increases. b) the motion of the particles decreases. c) the particles collide less frequently. d) the pressure exerted by the particles on the walls of the container decreases. e) b, c, and d.
e) b, c, and d
Which of the following phases of matter can transfer heat by convection? a) liquids b) solids c) gases d) both a and b e) both a and c
e) both
A colligative property depends on _________________________. Question options: a) the identity of the solute b) the concentration of the solution c) the number of solute particles dissolved in the solution d) both a and b e) both b and c
e) both b and c
What is true about chemical reactions? Question options: a) They proceed at the same rate unless one or more conditions is/ are changed. b) A certain amount of energy, called the activation energy, must be supplied for the reaction to occur. c) Increasing the surface area increases the rate of reaction. d) Pressure has no effect on reactions involving gases. e) both b and c
e) both b and c
What effect does a catalyst have on reaction rate? Question options: a) It has no effect. b) It increases the reaction rate. c) It decreases the reaction rate d) It lowers the activation energy e) Both b and d.
e) both b and d
The change from liquid to gas is called ________. a) condensation b) deposition c) evaporation d) vaporization e) both c & d
e) both c & d
Clay beads for making a bracelet are being baked in an oven. If the system is defined as the clay beads and the surroundings as the air in the oven, is this an endothermic or exothermic process?
endothermic
Examine this reaction: H2 + I2 + 50.2 kJ → 2HI This reaction is __________________.
endothermic, with a positive ΔH
q=mc∆T : q=∆H if q absorbes heat, it will be positive q= heat m= mass c= specific heat delta T= change in temp
enthalpy!
If the temperature changes from 19°C to 37°C during a chemical reaction, the reaction is ________, and q is ________ .
exothermic, positive
Examine this reaction: C (s) + 2 (g) → CO2 (g) + 393 kJ This reaction is __________________.
exothermic, with a negative ΔH
Which of the following are characteristics of heat? Question options: a) heat moves from a warmer body to a cooler body b) heat moves from a cooler body to a warmer body c) heat is the ability to transfer thermal energy d) heat can be transferred by conduction, convection, or radiation e) all of the above f) a, c and d
f) a, c, and d
Hess's Law can be used to determine the heat of reaction in the lab.
false
The standard heat of formation for gaseous CO is zero.
false (CO is not an element, so it has anonero heat of formation)
The standard heat of formation for liquid nitrogen is zero.
false (nitrogen is not liquid at standard state)
Clay beads for making a bracelet are being baked in an oven. The heat is flowing __________.
from the air in the oven to the beads
Stronger intermolecular forces =
greater surface tension
exothermic -∆H has...
high entropy +∆S negative enthalpy -∆H
A solution can be classified as a _________.
homogeneous mixture
collision theory
in order to react, molecules must collide! requirements: must collide must have sufficient kinetic energy must collide with proper geometry
As the concentration of a solution _______, the vapor pressure _______.
increases, decreases
Does the entropy (△S) increase or decrease in each of the following processes? The wind blows a pile of leaves all over the yard. As you are pumping gas into your car, gas fumes escape into the air.
increasing, increasing
The melting point of a solid ____________.
is the point at which the energy of vibrational movement of the particles is greater than the attractive forces between the particles.
According to the kinetic-molecular theory, ________. Question options: a) solids have less kinetic energy at a given temperature than gases b) liquids have less translational movement than gases c) the particles in a liquid or solid are larger than the particles in a gas d) the particles in solids, liquids, and gases do not attract each other e) all of the above
its not A or E i got this one wrong
The molal freezing point constant and molal boiling point constant depends on which of the following? a) the identity of the solute b) the normal freezing point and boiling point of the solvent c) the identity of the solvent d) the concentration of the solution e) temperature
its not a i got it wrong
As a liquid is warmed, it becomes ____ (more/less) dense, and ____ (rises/sinks).
less, rises
The vapor pressure of a solution is ______ than the vapor pressure of the pure solvent.
lower
mass percent
mass of a solute/mass of a solution x 100%
Solid to liquid
melting
Two substances that are soluble in each other in all proportions are called
miscible
Which concentration unit is used in colligative property calculations?
molalality
If liquid A has a lower vapor pressure than liquid B, ______________. Question options: a) liquid A evaporates more easily than liquid B b) liquid A has lower intermolecular forces than B c) liquid A has a higher boiling point than B d) both a and b e) both b and c
not A or B I got this one wrong
For a solid and a gas which are at the same temperature, ________________. Question options: a) the gas has more kinetic energy than the solid b) the solid has more kinetic energy than the gas c) the gas and the solid have the same amount of kinetic energy d) much of the solid's kinetic energy is due to vibrational motion, while the gas has much translational energy e) both c and d
not A or D i got this one wrong too
Which of the following is a formation reaction? Question options: a) 2 S (s) + 3 O2 (g) → 2 SO3 (g) b) 2 Na (s) + Cl2 (g) → 2 NaCl (s) c) S (s) + O2 (g) → SO2 (g) d) C (l) + O2 (g) → CO2 (g) e) both c and d
not E or D i got it wrong
Ionic compounds have a larger effect on colligative properties than molecular compounds because
one mole of an ionic compound releases more particles into solution than one mole of a molecular compound.
colligative properties
porperties of a solution that depend on the # of solute particles in a dissolved solution and not the identity
Examine this chemical reaction and answer the question that follows: 6 CO2 + 6 H2O + Energy → C6H12O6 + 6 O2 In this photosynthesis that occurs in plants, is ΔH positive or negative?
positive
Using this solubility curve, answer the following question. Indicate whether the following solution is saturated, unsaturated, or have the potential to be supersaturated a the given temperature. 55 g of NH4Cl at 40°C
potentially supersaturated
Water in a swimming pool being warmed by the sun is an example of the transfer of thermal energy by __________.
radiation
A solution that contains the maximum amount of solvent that can be dissolved is called ________________.
saturated
Using this solubility curve, answer the following question. Indicate whether the following solution is saturated, unsaturated, or have the potential to be supersaturated a the given temperature. 10 g of KClO3 in 100 g of water at 20°C
saturated
Using this solubility curve, answer the following question. Indicate whether the following solution is saturated, unsaturated, or have the potential to be supersaturated a the given temperature. 30 g of KCl at 10°C
saturated
Solids are not fluid because _______________. a) the particles strongly attract each other b) the particles are too close together c) the particles do not have much kinetic energy d) the particles are much larger than those in gases. e) all of the above.
something other than B and C i got it wrong
The change from solid to gas is called __________.
sublimation
solid to gas
sublimination
in calorimetry, the water is the ____
surroundings
in calorimetry, the dissolved substance is the ____
system
The surface tension on the surface of a liquid can be explained by ____________.
the attraction of the particles to each other in the liquid
Heat transfer by convection is based on ______________.
the current set up when the density of a substance changes as it warms or cools
freezing point depression
the difference in temperature between the freezing point of a solution and the freezing point of the pure solvent
The relatively low vapor pressure of water can be explained by _____________.
the large attraction of the water molecules to each other
What is solubility?
the number of grams of a substance soluble in 100 g of water at a given temperature.
Gases can assume the shape and volume of its container because
the particles can move past one another.
Solids conduct heat better than gases. According to the kinetic-molecular theory, this is because __________.
the particles in the solid are much closer together than the particles in the gas.
In the dissolving process for an aqueous solution, _________________________________________.
the solute breaks apart into separate molecules or ions in solution
At the boiling point of a liquid __________.
the vapor pressure is equal to the atmospheric pressure
Gases are compresible because
they have more free space between particles compared to liquids and solids
conduction
transfer of thermal energy between particles of matter (hot iron, cookie sheet, snow)
The standard heat of formation for solid copper is zero.
true
entropy increases if the product is greater than reactants
true
entropy increases when the thing breaks up into small parts
true
entropy increases with temp
true
Using this solubility curve, answer the following question. Indicate whether the following solution is saturated, unsaturated, or have the potential to be supersaturated a the given temperature. 130 g of KI in 100 g of water at 30°C
unsaturated
To convert from one pressure unit to another...
use 760 mm/1 atm or 1 atm/760 mm
liquid to gas
vaporization
direct relationship
when one variable increases, so does the other
indirect relationship
when one variable increases, the other decreases
A system that gives off heat to its surroundings is called exothermic.
yes
for more of ^ look at 11.6 quiz
yup!
Consider the reaction H2 (g) + Br2 (l) → 2 HBr (g). If △S = 114JKmol, what is △S for the reverse reaction, 2 HBr (g) → H2 (g) + Br2 (l) ?
ΔS = - 114 kJ/K•mol for the reverse reaction.
Gibbs free energy equation
∆G = ∆H - T∆S
how much heat is required to melt 400 g water?
∆Hf= 334 J/g and ∆Hv = 2260 J/g Q= (400 g)(334 J/g)= 133600
∆Tf = Kf x m
∆Tf = magnitude of freezing point depression Kf= molal freezing point depression constant m= molality
