Chm 11-12 test
Charles' law
Vi × Tf = Vf × Ti
Avogadro's law
Vi × nf = Vf × ni
Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g) How many grams of Zn is required to produce enough H₂ to fill a 50 L cylinder to a pressure of 10 atm at 25°C?
g = (MMPV)/(RT) ((65.39g/mol)(10atm)(50L))/((0.0821)(298.15°K))=1335g
The ideal gas law (PV = nRT) provides relationships among pressure, volume, amount, and temperature of a gas inside a container. Rewrite the ideal gas law solving for temperature, T. t= PV/nR t= nRV/P t= P/nRV t= nR/PV t= nRP/V
t= PV/nR To solve for temperature, T, both sides of the ideal gas law are divided by the product, nR, where n is the number of moles of gas and R is the ideal gas constant. So the temperature is directly proportional to the pressure and the volume of gas and inversely proportional to n, the moles of gas.
Entropy
the degree of disorder or uncertainty in a system
Why does the solubility of most substances increase as the temperature increases?
the energy added to the solution breaks the solute-solute bonds and solvent-solvent bonds allowing them to disperse evenly.
freezing point depression boiling point depression
∆Tf = (Kf)(mole of solution particles)÷(Kg of solvent) ∆Tb = (Kb)(mole of solution particles)÷(Kg of solvent)
You want to use 0.520 moles of KBR to prepare a 2 molarity KBR solution. How many milliliters of solution do you prepare?
(0.520mol)(1L)/(2mol/L)=.26L (0.26L)(1000)=260mL
How many moles of LiOH do you have in 400 mL of 3.25 molarity LiOH
(3.25mol/L)(0.4L)=1.3mol
4.9 g of sugar is dissolved in 300 g of water. What is the mass percent of sugar in the solution?
(4.9g/304.9g) × 100 = 1.61%
What is the final concentration of the solution prepared by diluting 52 mL of 8.0 molarity HBr to a final volume of 2 L?
(Molarity solution) × (Volume solution) = (Molarity dilute solution) × (Volume dilute solution) ((8mol/L)×(0.052L))=((Molarity dilute solution)×(2L)) ((8mol/L)×(0.052L))/(2L)=0.208mol/L
The initial volume of the gas container is 750 mL. If the pressure of the gas container changes from 84 mmHg to 360 mmHg. What is the final volume of the gas?
(Pi x Vi )/(Pf ) = Vf (0.111atm x 0.75L)/(0.474atm)=0.18L
What is the final volume of a 1.00L system initially at 315°K and 1.1 atm final conditions are STP
(Pi x Vi x Tf )/(Pf x Ti) = Vf (1.1atm x 1L x 273.15K)/(1atm x 315K)= 0.95L
What is the final pressure (atm) of a system with a volume increase from 0.75L to 1.1L with an initial pressure of 1.25 atm?
(Pi x Vi)/Vf = Pf (1.25 x 1.1)/1.1= 0.85
Assuming pressure and temperature remains constant what is the final volume of a gas when the initial number of moles of the gas in a 2 L vessel is double?
(Vi x 2nf )/(ni) = 2Vf 2L × 2= 4L
The number of moles of a gas in a 3 L container is tripled, what is the final volume of the gas (pressure and temperature remains constant).
(Vi x 3nf )/(ni) = 3Vf 3L × 3= 9L
What is the final volume of a gas that initially occupies 2.50L at 298°K and it is heated up to 321°K
(Vi x Tf )/(Ti) = Vf (2.5L x 321K)/(298K)=2.69L
What is the initial temperature in Celsius of a gas if the volume change from 1 L to 1.1 L and the final temperature is 255°C.
(Vi x Tf )/(Vf) = Ti (1L x 528.15K)/(1.1L)=480K - 273.15 = 207C
A 100.-mL sample of aqueous sulfuric acid, H2SO4, is titrated using 0.200 M KOH. Using an indicator that changes color after all the sulfuric acid protons have reacted with the OH− ions, the solution changes color when 32.50 mL of KOH has been added. What is the molar concentration of the sulfuric acid? 0.813 M H2SO4 32.5 M H2SO4 0.130 M H2SO4 0.0650 M H2SO4 0.0325 M H2SO4
0.0325 M H2SO4 step 1: the balanced equation is written first. step 2: then the amount of KOH is converted to moles step 3: using the moles of KOH, the moles of H2SO4 are calculated. step 4: Finally, the moles of H2SO4 are converted to molarity
How many moles of NH4NO3 are there in 75.0 mL of 2.30 M NH4NO3? 30.7 mole NH4NO3 172.5 mole NH4NO3 0.0307 mole NH4NO3 0.173 mole NH4NO3 0.0326 mole NH4NO3
0.173 mole NH4NO3 To calculate the number of moles of NH4NO3, first the milliliters of solution are converted to liters (75.0 mL = 0.075 L) and then the molarity is used as a conversion factor.
If one atm equals 760 mmHg. What is .4 ATM in terms of mmHg?
0.4 × 760 = 304
Examine the graphs of solubility in water versus temperature given below. Which of the following statements are true? 1. KBr is more soluble than NH4Cl for all temperatures. 2. Glucose is more soluble than LiCl for all temperatures. 3. More Ce2(SO4)3 dissolves is cold water rather than warm water. 4. CH3CO2Na is more soluble than NaNO3 at 60°C. Graph 2 and 3 1 and 2 2 and 4 3 and 4 1 and 3
1 and 3 Number 1 is true since the graph shows that both KBr and NH4Cl increase in solubility as the temperature increases. Their rates of increase in solubility is about the same, but KBr is always about 20 grams more soluble per 100 g water than NH4Cl. Number 3 is also true. While Ce2(SO4)3 is not very soluble at any temperature, almost 20 grams dissolve per 100 grams of water at 0 °C and almost no Ce2(SO4)3 dissolves at 40 °C. Number 2 is false up to approximately 15 °C, LiCl is more soluble than glucose and then the solubility reverses. Number 4 is also false - at 60 °C per 100 grams water approximately 110 grams CH3CO2Na dissolve and over 120 grams NaNO3.
Which of the following processes occur with an increase in entropy? 1. Dissolving of sugar in water 2. Freezing of water 3. Obtaining pure oxygen by extracting it from air 4. A department store on the day after Christmas 2 and 4 2 and 3 1 and 4 1 and 2 3 and 4
1 and 4 Entropy is a measure of the amount of disorder or randomness in a situation. Number 1, dissolving of sugar in water, occurs with an increase in entropy because the sugar molecules, which in the solid state are arranged in an organized crystalline structure, become less ordered when mixed with water in the solution. Number 4, a department store on the day after Christmas, is a fairly chaotic event. The store is very crowded and there is merchandise being purchased, returned, trampled upon, etc. Numbers 2 and 3 are both changes to a more orderly process. The freezing of water converts the liquid state, which is relatively disordered since the water molecules are constantly moving past each other, to a more rigid, organized form, the solid state. Obtaining pure oxygen by extracting it from air also decreases the entropy because oxygen has only one element while air is a mixture of several gases.
How would you prepare 9.7 g of PbCl₂ from a 0.1 molarity solution of Pb(NO₃)₂ and a 0.2 molarity solution of CaCl₂?
1) Pb(NO₃)₂ + CaCl₂ → PbCl₂ + Ca(NO₃)₂ 2) (9.7g PbCl₂)/(278.1g/mol)=0.035mol 3) (0.035mol)/(0.1mol/L Pb(NO₃)₂)=0.35L Pb(NO₃)₂ 4) (0.035mol)/(0.2mol/L CaCl₂)=0.17L CaCl₂
steps in the dissolution of a solute and how to determine if it dissolves.
1) Solute-separation: overcome solute-solute attraction ∆E positive 2) Solvent-separation: overcome solvent-solvent attraction ∆E positive 3)solvation step: as solute-solvent attractive forces develop, energy is released, making ∆E negative
The following list of solutions contain water, sometimes as the solute and other times as the solvent. Identify the solutions that have water as the solvent. 1. Maple syrup 2. Rubbing alcohol (70% isopropyl alcohol) 3. The air in a room where a humidifier is being used 4. Cola soft drink 5. Sea water 1, 4, and 5 1 and 4 2, 3, and 5 2 and 3 4 and 5
1, 4, and 5 Numbers 1, 4 and 5 are all solutions with water as the solvent. Number 1, maple syrup, has sugars and flavoring dissolved in water. Number 4, a cola soft drink, has a water base with sugar, flavors and carbon dioxide gas dissolved in water.
Micelles are spherical structures that form when soap molecules are added to water. Choose the statements that are true about micelles. 1. The outside of the micelle is formed from the polar heads of soap molecules and it is hydrophilic. 2. The outside of the micelle is formed from the polar heads of soap molecules and it is hydrophobic. 3. The inside of the micelle is formed from the nonpolar tails of soap molecules and it is hydrophilic. 4. The inside of the micelle is formed from the nonpolar tails of soap molecules and it is hydrophobic. 5. Grease molecules dissolve inside the micelle and the micelle dissolves in water, so that the grease may be washed away. 2 and 3 1 and 4 2 and 4 2, 3, and 5 1, 4, and 5
1, 4, and 5 The outside of the micelle needs to be polar, since it is in contact with water molecules and is therefore hydrophilic ""water-loving"" (number 1). The inside of the micelle, on the other hand, contains the nonpolar hydrocarbon tails of the soap molecules; so it is hydrophobic ""water-fearing"" (number 4). Number 5 is also true, grease molecules are nonpolar and therefore not water-soluble. To be able to be dissolved in water, they need to be encapsulated in the micelle.
If a balloon that cannot expand any further is filled with helium at a pressure of 1.10 atm and a temperature of 15.0°C, what will be the pressure if the temperature rises to 35.0°C? 1.18 atm 2.57 atm 0.471 atm 1.03 atm 97,574atm
1.18 atm sing the initial-condition/ final- condition equation and cancelling the number of moles and the volume which are constant, and solving for final pressure
The gas in a pressurized container is at 1200 millimeters of mercury. What is the gas pressure in atmospheres? (Assume 3 significant figures in the pressure.) 1.58 atm 912,000 atm 1200 atm 47.2 atm 3048 atm
1.58 atm To convert from millimeters of mercury to atmospheres, you use the conversion factor (1 atm = 760 mm Hg).
What must the temperature (in °C) be, if 50.0 grams of O2 in a 10.0 L container has a pressure of 5.0 atm? 117 °C 390 °C 273 °C 12.2 °C −261 °C
117 °C To calculate the temperature, one must first solve for T in the ideal gas equation, then substitute the appropriate values for pressure, number of moles and volume into the equation and calculate the answer. Since the amount of O2 was given in grams and should be in moles in the ideal gas equation, that conversion must be made. This answer is in kelvins which must then be converted to degrees Celsius.
Examine the graphs of solubility in water versus temperature given below. Using the solubility information, calculate how many grams of NH4Cl can dissolve in 250 grams of water at 60°C? Graph 455 grams NH4Cl 22.0 grams NH4Cl 55 grams NH4Cl 2.58 grams NH4Cl 138 grams NH4Cl
138 grams NH4Cl The graph indicates that approximately 55 grams of NH4Cl dissolve for every 100 grams of water at 60°C. The calculation is as follows:
How many grams of sulfur dioxide (SO2) are found in a 3.50 L container at 100. °C and a pressure of 2.00 atm? 14.7 grams SO2 4.37 grams SO2 280 grams SO2 54.6 grams SO2 0.853 grams SO2
14.7 grams SO2 One must first convert the temperature from the Celsius to the Kelvin scale and then substitute the appropriate values for temperature, pressure, and volume into the equation and solve for the moles. The moles must then be converted to grams.
Select the heterogeneous mixtures from the following: 1. white gold 2. a strawberry shake made with fresh strawberries 3. ginger ale 4. oxygen and nitrogen gases 5. oil in water 2 and 5 1 and 4 1, 3, and 5 2, 4, and 5 2, 3, and 4
2 and 5 Numbers 2 and 5 are both heterogeneous mixtures. Number 2, a strawberry shake made with fresh strawberries, will have the strawberry seeds and other particles separate from the rest of the pulp, milk, ice cream, and other ingredients. Number 5, oil and water, is also a heterogeneous mixture since oil does not dissolve in water and two separate layers occur. Number 1 is a solution because the mixture of gold with other metals is made by melting all the metals so that they can mix at the atomic level. Number 3 is a solution because ginger ale combines sugar, flavors and dissolved carbon dioxide in water. Number 4 is also a solution because gas particles are constantly moving in a random fashion, and are therefore able to mix with each other.
A gas is placed in a container at a certain pressure and then conditions change so that the pressure is doubled. Which of the following changes would double the pressure? 1. Doubling the volume. 2. Reducing the volume to one-half. 3. Doubling the temperature (Kelvin scale). 4. Reducing the temperature (Kelvin scale) to one-half. 5. Both the volume and temperature (Kelvin scale) would need to be changed at the same time. 2 or 3 1 or 3 1 or 4 2 or 4 5
2 or 3 Either decreasing the volume to one-half or doubling the temperature doubles the pressure. This is so since pressure is inversely proportional to volume, so an increase in pressure comes with a decrease in volume. Also pressure is directly proportional to temperature, so an increase in pressure comes with a proportional increase in temperature.
What volume of 2.20 M HCl must be added to enough water to prepare 4.70 liters of 1.06 M HCl? 2.26 L 0.496 L 2.02 L 9.75 L 0.442 L
2.26 L In this case we must start with what the final concentration and volume - 1.06 M and 4.70 L. We first need to determine how many moles of HCl are in this desired solution, then find what volume of the stock solution (2.20 M HCl) has the same number of moles of HCl.
What mass of WATER is contained in 225 grams of 4.30 mass % MgS solution? 52.3 grams H2O 215 grams H2O 225 grams H2O 9.68 grams H2O 1.90 grams H2O
215 grams H2O To calculate the amount of water in the solution, one first calculates the amount of magnesium sulfide. Then subtracting from the total mass of the solution: 225 g solution 9.68 g MgS = 215 g water
1mole of any gas at STP occupies what volume.
22.4L
A certain volume of gas is in a closed chamber. The pressure of the gas is double, what happens to the temperature?
2V α 2T
Calculate the total energy change, Etotal, for a solution of an ionic solid, if Esolute separation, the separation of the ionic solid into ions, requires 750. kJ, and the opening of spaces for the water molecules requires 96 kJ (Esolvent separation). Esolvation, forming the solution, releases 475 kJ. 179 kJ − 1321 kJ 1321 kJ 371 kJ − 371 kJ
371 kJ Steps 1 (solute separation) and 2 (solvent separation) require energy, so the values for E are positive. Step 3 (solvation) releases energy, giving a negative E value. Etotal is calculated as follows: Etotal = (Esolute separation + Esolvent separation ) − Esolvation Etotal = (750 kJ + 96 kJ) − 475 kJ Etotal = 371 kJ
How much alcohol is contained in 500 mL of an alcohol-water solution that is 8.50 vol% alcohol? 58.8 mL alcohol 492 mL alcohol 4250 mL alcohol 42.5 mL alcohol 1.7 mL alcohol
42.5 mL alcohol To calculate the amount of alcohol in the solution, the 8.50 vol % is used as a conversion factor.
A flexible cylinder contains 10.0 liters of helium gas at 350 K under a pressure or 15.0 atm. What is the final volume if the pressure is lowered to 5.00 atm and the temperature is changed to 500 K? 42.9 liters 2.33 liters 21.0 liters 4.76 liters 4.29 liters
42.9 liters To convert from one set of conditions to another, the initial-condition / final condition gas equation is used. This equation is
A 2.56 g sample of an unknown gas is inside a 5.20 L container under at 25.0°C and 163 mm Hg. What is the molar mass of this gas? 56.0g/mol 0.0739g/mol 4.70 g/mol 0.00620 g/mol 0.0179 g/mol
56.0g/mol To calculate the molar mass, the idealgas equation is used.
Suppose the following chemical reaction takes place at 25.0 °C and 1.25 atm. C4H8(g) + 6 O2(g) -> 4 CO2(g) + 4 H2O(l) If you start with 1 mole of butane (C4H8) and excess oxygen, calculate the volume of carbon dioxide (CO2) produced. Assume 100 % yield. 78.3 liters 6.57 liters 19.6 liters 97.8 liters 954 liters
78.3 liters The balanced chemical equation gives the ratios of moles of the reactant and products. It shows that for every 2 moles of butane (C4H8), 4 moles of carbondioxide are produced.
Calculate the density of argon gas at a temperature of 300.°C and a pressure of 10.0 atm. 8.48g/L 0.213g/L 39.9g/L 0.118g/L 16.2g/L
8.48g/L The formula for the density of any ideal gas is as follows.
How many grams of KBr are there in 52.8 mL of a 1.40 M KBr solution? 8.80 g KBr 0.0739 g KBr 0.621 g KBr 167 g KBr 3.16 g KBr
8.80 g KBr To calculate the number of grams of KBr in the solution, one must first calculate how many moles there are in the 52.8 mL of solution and then convert the moles of KBr into grams. This can be done through a series of conversions:
A) How many moles of CaF2 are there in 25mL of 0.35 molarity CaF₂. B) reverse, what volume at 0.35 molarity is required to obtain 0.00875 moles.
A) (0.350mol/L)(0.025L)=0.00875mol B) (0.00875mol)/(0.350mol/L)= 0.025L
Consider the reaction 2SO₂(g) + O₂(g) → 2SO₃(g) A) what volume in liters of O₂ gas at STP is required to produce 2 moles of SO₃ sulfur trioxide? B) what volume in liters of O₂ gas at 25°C and 1 atm pressure is required to produce two moles of SO₃ gas?
A) (1mole * 0.0821* 273.15)/(1atm) =22.4 B) (1mole * 0.0821* (25+273.15))/(1atm) =24.5
10.0 grams of a gas are in a rigid sealed container at a pressure of 450 mm Hg. The container is punctured and a small hole forms on the side of the container. If the container is in a room with normal atmospheric pressure, what happens? Air rushes into the container because atmospheric pressure (760 mm Hg) is greater than the pressure inside the container. Gas rushes out of the container because the gas has been trapped in the sealed container and needs to expand and mix with the air outside. There is no movement of gas particles from the container nor outside air moving in. The volume of the container decreases as the gas particles inside rush out once the container is punctured. The volume of the container increases as the gas particles inside rush out once the container is punctured.
Air rushes into the container because atmospheric pressure (760 mm Hg) is greater than the pressure inside the container. Gas particles are constantly moving and colliding with the sides of container, whether the gas is the substance inside the container or the molecules of the different gases found in the atmosphere. Initially, the pressure is higher outside the container so more molecules from the air outside will move through the hole in the wall of the container and enter than particles of the gas inside the container will move out. The molecules of the gas inside are at a lower pressure and therefore will find the hole less often. Eventually the pressures inside and outside will equalize and particles will move in and out of the container at the same rate.
how to calculate % composition a) by mass b) by volume
a) (Grams of solute)/(Grams of solution) b) (Volume of solute)/(Volume of solution) c) (Grams of solute)/(Volume of solution)
How is solubility affected by a) temperature b) pressure
a) for solids and liquids, solubility increases with temperature. for gas, solubility decreases with temperature. b)for solids and liquids, solubility is relatively unchanged with pressure change. for gas, solubility increases with an increase in pressure.
Under certain conditions, different gases behave in a similar manner. This approximation is the basis for what is described as an ideal gas. All of the following are descriptions of the behavior of ideal gases EXCEPT: In an ideal gas, polar molecules sometimes travel together as a pair or in a small group as droplets. In an ideal gas, molecules are constantly moving in random directions. In an ideal gas, molecules do not attract or repel each other. In an ideal gas, when molecules collide with other molecules, they bounce off and change direction. In an ideal gas, the molecules move in a straight line path until they collide.
In an ideal gas, polar molecules sometimes travel together as a pair or in a small group as droplets. This is NOT a true statement, ideal gases do not exhibit intermolecular forces attraction; therefore, they move as single molecules in random directions until they collide with another molecule or the wall of the container, when the molecule changes direction and continues its movement.
How many liters of 2.5 molarity solution Can be made from 300 g K₂S
K₂S = ((300g)/(112.26g/mol)) =2.72mol ((2.72mol)/(2.5mol/L))= 1.09
define and calculate molarity
M= (moles of solute) ÷ (1L of solution)
a 1.89 g sample of A noble gas is stored in a 1.0L vessel at 874 mmHg and 25°C. What is the noble gas?
MM = (gRT)/(PV) ((1.89g)(0.0821)(298.15°K))/((1.15atm)(1L))=40.2 argon
What is the molarity of a solution prepared by dissolving 15.2 g NaOH in 410 mL
NaOH = 15.2g/(40g/mol)=0.38mol (0.38mol/0.410L) = 0.93mol/L
The ideal gas law (PV = nRT) provides relationships among pressure, volume, amount, and temperature of a gas inside a container. If the Kelvin temperature in a container is doubled, which of the following changes may occur to keep the pressure constant? One-half of the amount of gas is removed from the container. The volume is cut in half. The volume is doubled and the amount of gas is doubled. The volume is cut in half and the amount of the gas is doubled. The overall effect cannot be determined without out knowing the numerical values involved.
One-half of the amount of gas is removed from the container. When the temperature is doubled the molecules of gas move faster than before. If there are no changes in the pressure or volume, then the number of particles would have to be decreased to one-half the original amount. The ideal gas law (PV = nRT)
What is the pressure of a 2 L flask containing .75 g of Ne at 25°C?
P = (nRT)/(V) ne = (0.75g)/(20g/mol) = 0.0375mol ((0.0375mol)(0.0821)(298.15°K))/(2L)=0.46atm
Ideal gas law and its relationships
P = (nRT)÷V a) P α T b) P α n c) P α (1/V) d) V α n e) V α T
A gas 1 L is in a sealed chamber containing a movable piston. If the piston is moved so that the volume of gas is compressed to a volume of .5 L , What will happen to the gas pressure?
P α 1/V 2P α (1/2)(1/V)
Gay-Lussac's law
Pi × Tf = Pf × Ti
Boyle's law
Pi × Vi = Pf × Vf
Combined Gas Law
Pi × Vi × Tf × nf = Pf × Vf × Ti × ni
What steps are simultaneously happening when a substance dissolves? For the substance (Solute) to dissolve what has to be the determining event?
Solute seperation solvent seperation solvation
STP
Standard temperature and pressure
In a solution produced from water and an ionic solid, several steps have to take place for the solvent and solute to mix together and form the solution. All of the following statements about the solution process are true EXCEPT: The breaking up of the ionic solid requires energy; this energy is recovered by the opening up of the solvent to make room for the ions. The ionic solid lattice is broken apart into positive and negative ions. Spaces are opened up in the solvent, water, to make room for the ions. The positive and negative ions move into the spaces created for them in the solvent. Energy is released when water molecules surround the solute ions.
The breaking up of the ionic solid requires energy; this energy is recovered by the opening up of the solvent to make room for the ions. This statement is not true. Both the breaking up of the ionic solid into the positive and negative ions and the opening up of the solvent to make space for the ions are endothermic steps, that is, they require energy. The solvent particles, water molecules in this case, are attracted to each other by intermolecular forces of attraction. These attractive forces must be overcome so that spaces between water molecules may develop.
Which of the following helps explains why a liquid in a closed container at a specific temperature has a constant proportion of gas molecules in the space above the liquid and no more or no less? vapor pressure volatility colligative property dynamic equilibrium static equilibrium.
dynamic equilibrium A liquid in a closed container has particles at the surface escaping into the gas phase above the liquid evaporation. At the same time, some of these gas molecules re-enter the liquid phase through condensation. When these two processes occur at the same rate, a dynamic equilibrium has been established.
Consider the following diagrams representing different gas samples, all at the same pressure. Assume the volume in #1 is exactly one-half the volume in #2 and in #3. The temperature is highest in #3 The temperature is highest in #1. The temperature is highest in #2. The temperature in #2 is the lowest of all. The temperatures in #1 and #2 are identical and higher than the temperature in #3.
The temperature is highest in #3 Using the ideal gas law: PV = nRT , we see that volume and temperature are directly proportional. As long as the pressure remains constant, if the volume increases, as it does in comparing #1 and #3, the temperature increases to match the increasing volume. Comparing #2 and #3, there are twice as many particles in #2 as in #3, so to maintain the pressure constant, the particles must move slower in #2. How fast molecules move is related to their temperature, so slower moving molecules are at a lower temperature than molecules that move faster.
It is possible to completely describe the behavior of an ideal gas using just four variables. Which of the following is NOT one of those four variables? electronegativity pressure volume temperature number of moles
electronegativity Electronegativity is related to an atom''s ability to attract to itself the shared electrons in a covalent bond, so this variable is not related to the behavior of an ideal gas.