Module 4 Chemical Reactions and Calculations
What is STP for a gas?
0 oC and 760 Torr
How many moles of O2 is needed to react completely with 0.35 moles of H2?
0.175
SO2 reacts with H2S as follows: 2H2S + SO2 --> 3S + 2H2O When 7.50 g of H2S reacts with 12.75 g of SO2, which statement is true?
0.221 moles of SO2 is consumed (WRONG) 0.266 moles of SO2 is consumed
If you had 0.35 moles of hydrogen gas (H2), how many moles of product (H2O) would you expect (assuming there is enough of the other reactant)?
0.35
SO2 reacts with H2S as follows: 2H2S + SO2 --> 3S + 2H2O When 7.50 g of H2S reacts with 12.75 g of SO2, which statement is true?
0.441 moles of H2O is generated (WRONG) 0.111 moles of H2O is generated
The pressure of a gas is 750.0 torr when its volume is 400.0 mL. Calculate the pressure (in ATM) if the gas is allowed to expand to 600.0 mL at constant temperature.
0.660 P1V1 =P2V2 (0.987 atm)(400.0 mL) = x (600.0 mL)
Converting moles to atoms Step 1: Molar Mass AgNO3 = 169.87 AgNO3 Find the compound's molar mass. (One mole of AgNO3 weighs 169.87 grams) Step 2: 169.87 AgNO3/ 1 Mol AgNO3 Select a conversion factor which places the unit you want to eliminate in the denominator and the unit you want to convert to in the numerator. Step 3: 240 AgNO3/_____ * 169.87 AgNO3/1 Mol AgNO3 Finally, eliminate the unit you do not want (in this case, grams) to get your answer in moles. 240 grams of AgNO3 = moles AgNO3
1.41
SO2 reacts with H2S as follows: 2H2S + SO2 --> 3S + 2H2O When 7.50 g of H2S reacts with 12.75 g of SO2, which statement is true?
10.6 grams of sulfur is generated
How much energy is contained in the reactants? How much energy is contained in the products? What is happening to the total energy of the molecules in the chemical reaction?
150 50 It's decreasing
Quiz 2.3 ATM (atmospheres) is equal to __________ mmHg
1800
SO2 reacts with H2S as follows: 2H2S + SO2 --> 3S + 2H2O When 7.50 g of H2S reacts with 12.75 g of SO2, which statement is true?
3.4 grams of H2S remains when reaction is complete (WRONG) 0.36 grams of SO2 remains when reaction is complete
In order to use the gas laws, you have to be able to convert between oC and K! 32 oC is ____________K
305
Compared to oxygen, how many moles of hydrogen and nitrogen are present in the compound? O 1.03 mol : H 5.20 mol = O 1 mol : H O 1.03 mol : N 2.06 mol = O 1 mol : N
5 2 To get the whole number mole ratio of elements in the compound, divide each of the elements, by the element with the smallest number of moles. For example, if we wanted to know the relative number of carbon atoms, we know that for 1.03 mol of oxygen, we have 4.12 moles of carbon. If we divide these two values, we can see that for every 1 mol of oxygen there are 3.99 or 4 moles of carbon.
The volume of a gas is increased from 150.0 mL to 350.0 mL by heating it. If the original temperature of the gas was 25.0 oC, what will its final temperature be in oC?
58.3 P/T=P/T Gay-Lussacs Law (WRONG)
How many joules are in 148 calories?
619
Butane is a highly combustible gas with the chemical formula C4H10. Butane is _____________ % carbon. Report your answer with 3 significant digits.
82.7
Method 1: Mole Comparison 1. Choose one reactant 2. Calculate how much of the other reactant(s) must be present to react completely with the one you chose. We were given ? of O2. If 3 moles of O2 were to be completely used, then, according to chemical equation, ? of H2 would be needed. Because we were only given ? of H2, we would not have enough H2 to use all 3 moles of O2 that we were given. This means that H2 is the ? . And in fact, O2 is the ?.
? - 3 moles ? - 6 moles ? - 5 moles ? - limiting ? - excess
To convert from moles of one substance to moles of another substance always look to the ? of the ? chemical reaction.
? - coefficients ? - balanced
Avogadros law
Avogadro's law shows the inverse relationship between V and number of moles of gas (n). We can represent this mathematically as: V/n=constant It can also be represented as: V1/n1 = V2/n2
Quiz An endothermic reaction takes place in a glass beaker. What will you feel when you touch the beaker?
B. The beaker will feel cold
A molecule has a molecular mass of 78 AMUs. It also has the empirical formula CH. What is the formula of the molecule?
C6H6
Mod 2 The empirical formula, on the other hand, shows the correct whole number ratio of atoms in a molecule but it does not show the correct number of atoms in that molecule. The molecular formula shows the correct ratio of atoms in a molecule and the correct number of atoms in that molecule. C6H12O6 CH3CO2H C4H10 C3H8
CH2O CH2O C2H5 C3H8
Select all of the chemical formulas that can be an empirical formula.
CHO CH3OH C2H8 C2H4O C2H6O ALL WRONG KJBVSKJBVK
One way to increase the pressure of a gas is:
Decrease the volume of its container
If you want to know the identity of an unknown substance, what type of formula would you most likely want to know? A. Molecular formula B. Empirical formula C. Structural formula
Either A or C
If the products have less energy than the reactants, ΔHrxn will be negative and the reaction will release energy (be exothermic). If the products have more energy than the reactants, ΔHrxn will be positive and the reaction will absorb energy (be endothermic). Using the images on the right, which of the following are true?
Energy is absorbed to break the bonds in the reactants Energy is released to form the bonds in the products More energy is released by forming the products' bonds than is absorbed to break the reactants' bonds
Endothermic reactions—are reactions where, overall, energy is absorbed. The word "endo" means within. That may help you remember that energy is taken in or absorbed.
Exothermic reactions—are reactions where, overall, energy is released. The word "exo" means outside. Keeping that in mind may help you remember that energy is released.
An empirical formula and a molecular formula differ in their atom-to-atom ratios.
False
Select which of the following are true based on what you've learned thus far. Select all that apply.
In a balanced chemical reaction, the number of atoms of each element is the same on both the reactants and products side. Stoichiometric coefficients can be added before reactants or products in a chemical equation to balance the equation. Stoichiometric coefficients represent the relative number of reactants and products involved in a chemical reaction.
What is the empirical formula weight ? C4H5N2O1 = __ AMU
It seems like the weight of the empirical formula is 97.10 amu. This is only half the weight of a molecule of the actual substance.
If the volume of a gas is constant, what happens to the pressure when the temperature of the gas increases?
Lussac's law states if the temperaure increases the pressure of that gas will also increase if the volume and number of molecules are kept constant
A compound is 21.20 % nitrogen, 6.06 % hydrogen, 24.30 % sulfur and 48.45 % oxygen. Determine its chemical formula.
NH₇S₂ N2H8SO4
Do you think the student's method of balancing the equation is valid?
No, because coefficients weren't used to the balance the equation. No, because the products are no longer water and carbon dioxide. No, because the subscripts of molecules were changed to balance the equation.
Does your initial reaction still seem accurate? Select all that apply.
No, because the equation defies the law of conservation of mass. No, because the number of oxygen atoms on the reactants side is not the same as on the products side.
Boyle's Law The pressure of a gas is inversely proportional to the volume of that gas (for a given mass of a substance under constant temperature and in a sealed container).
P x V = constant P1V1= P2V2
When your body burns 1 gram of sugar completely, how much heat is released compared to burning the same amount of sugar in a flame?
The amount of energy released is the same
Which of the following is true?
The container with gas A will contain the just as many molecules as the container with gas B
Gay-Lussac's Law
The pressure of a gas is directly proportional to its temperature (for a given mass of gas at constant volume in a closed container). P x T = constant P1/T1 = P2/T2 (T↑ P↑)
What do the subscripts in a chemical formula represent?
The simplest mole and/or atom ratio of the elements in a compound
Let's say you have a flexible/expandable container of 2 moles of oxygen gas at a volume of 15 L in a container at 274 K at 3 atm. You leave the container in the lab overnight and the next day, the pressure in the container is still 3 atm and there are still 2 moles of oxygen but the volume has increased to 17 L. What prediction can you make about the temperature of the gas described above?
The temperature probably increased
Based on Avogadro's law, what would you predict will happen to the volume of a flexible container if the number of gas particles decreases?
The volume of the container will decrease; it will shrink
CxHy The empirical formula of benzene is CH and it has a molecular formula weight of 78 amu.
The weight of the empirical formula CH is 13 amu. The weight of the molecular formula is 6 times that amount or 78 amu. Therefore, you should multiply the all subscripts in the empirical formula by 6 to get the molecular formula.
For this same reaction, select all the statements that are true:
There is a net decrease in enthalpy The reaction is exothermic: ΔHrxn <0
Charles Law The temperature and volume of a gas are directly proportional (for a given mass of a substance under constant pressure and in a sealed container).
V x T = constant V1/T1= V2/T2 direct (T↑ V↑)
The pressure would decrease because gas molecules are moving slower and colliding less fequently with the walls of the container.
Which of the following statements summarizes the direct relationship between the temperature (T) and pressure (P) of a gas given a constant amount of gas at constant volume (V)?
Mod 5 When the H-H bonds in hydrogen gas break, energy is ?. When the Cl-Cl bonds on the reactants side break energy is ?. When the two new H-Cl bonds are formed in the products, energy is ?.
absorbed absorbed released
Energy is ? in the overall reaction. The products have ? than the reactants. The reaction is ?.
being released less enegery exothermic
In a chemical reaction, your "recipe" comes from the ? in a ? chemical reaction!
coefficients balanced
Notice that Khan keeps calling Fe2O3 iron(III)oxide. Do you remember how to name chemicals? Try one! Name CuI2
copper(II)iodide
Charles's law states that there is a ? relationship between temperature and volume. Charles's law applies when both ? are constant. In other words, when the temperature of a gas increases, the volume of that gas will ?. This only applies when the walls of the container are flexible.
direct pressure and number of increase
https://brainly.com/question/11522371 http://mmsphyschem.com/empForm.htm https://scilearn.sydney.edu.au/fychemistry/calculators/empirical_formula.shtml
https://www.quora.com/A-compound-is-24-7-calcium-1-2-hydrogen-14-8-carbon-and-59-3-oxygen-What-is-the-empirical-formula-and-name-the-compound https://www.convertunits.com/from/grams+Nitrogen/to/moles https://socratic.org/questions/the-empirical-formula-of-a-compound-is-ch-if-the-molar-mass-of-this-compound-is-
Method 2: Theoretical Yield Calculates how much of a particular product can be made. When considering more than one reactant, the limiting reactant is the one that produces the lowest theoretical yield. Using the second method, determine the limiting reactant and enter the theoretical yield of water vapor for the reaction below.
https://www.youtube.com/watch?v=clzZL0Szwo4
When a reaction releases energy, its products have ? energy than the reactants. Therefore the ΔH value** of the reaction will be ?. This is a sign of an ? reaction. When a reaction absorbs energy, its products have ? energy than the reactants. Therefore the ΔH value** of the reaction will be ?. This is a sign of an ?reaction.
less negative ex more positive en
Glucose is consumed in the presence of oxygen to afford carbon dioxide and water as shown in the balanced reaction: 6O2 + C6H12O6 --> 6CO2 + 6H2O If one mole of Glucose is allowed to react with 5 moles of oxygen, which statement is correct?
oxygen is the limiting reactant
This is an example of a ? reaction.
single replacement
Mod 4 Boyle's law states that for a given mass of gas at a constant ?, increasing the ? of a gas causes a ? in the pressure that gas. This is an example of an ? relationship.
temp vol decrease inverse (V↑P↓)
How does a calorie relate to a Joule?
C. A calorie represents a much larger amount of energy than a Joule
Keeping the ratio in mind, which of the following keeps that ratio while also having a molecular weight of 194 amu?
C8H10N4O2 = 194 amu Although the number of atoms in the molecular formula is twice as much as in the empirical formula the ratio between the number of atoms stayed the same. The ratio 8:10:4:2 in the molecular formula matches the ratio in the empirical formula—4:5:2:1.
Quiz An empirical formula and a molecular formula are always different
False
Glucose is consumed in the presence of oxygen to afford carbon dioxide and water as shown in the balanced reaction: 6O2 + C6H12O6 --> 6CO2 + 6H2O If one gram of Glucose is allowed to react with 1 gram of oxygen, which statement is correct?
Glucose is the limiting reactant
SO2 reacts with H2S as follows: 2H2S + SO2 --> 3S + 2H2O When 7.50 g of H2S reacts with 12.75 g of SO2, which statement is true?
H2S is the limiting reagent
What quantity would you use to convert mass to number of moles for use in calculations?
Molar mass
As the gas molecules increase, the volume of the container ?. This indicates a ? relationship between the number of gas molecules (in moles) and the volume of the container. This applies as long as the ? are held constant.
increases direct pressure and temp
Mod 3 Take a moment to consider how many hydrogen ions (H+) will be necessary to completely react with the following amounts of carbonate ion (CO3-) and then enter your responses below: Five carbonate ions - ? 1,500 carbonate ions - ? 2 x 1015 carbonate ions - ? 6.022 x 1023 carbonate ions - ? Three moles of carbonate ions - ?
10 H+ ions 3000 H+ ions 4000000000000000 H+ ions 1.204e24 H+ ions 6 moles of H+ ions Keep in mind that according to the balanced equation, twice as many hydrogen ions as carbonate ions will be required. There were some issues with your response: The mole ratio of hydrogen ions to carbonate ions is 2:1—that means you must have double the amount of hydrogen as carbonate. Look again at the mole ratio between carbonate ions and hydrogen ions. You don't appear to have taken it into account. You'll need more hydrogen ions to react with five carbonate ions. You don't have enough hydrogen ions to react with 1,500 carbonate ions. You need more hydrogen ions to react with 6.022 x 1023 carbonate ions. For the last question, you need to report the number of moles of H+ ions needed to completely react with 3 moles of CO3-. For this problem, you do not need to find the number of H+ ions, just the number of moles of H+
The ? reactant is always the reactant that is consumed ?. The ? reagent is always the reagent that is left over at the end of the reaction. Your theoretical yield is the amount of ? that can be produced from the ? reactant.
? - limiting ? - first ? - excess ? - product ? - limiting
A. device used to measure the heat absorbed or released during a chemical reaction or physical change B. Quantity of heat needed to raise 1 gram of water by 1 oC C. The SI unit of energy D. heat content of a system at constant pressure E. The amount of energy needed to increase the temperature of 1 gram of a substance by 1 oC F. The amount of energy needed to raise the temperature of an object by 1 oC
A - Calorimeter B - Calorie C - Joule D - Enthalpy E - Specific Heat F - Heat Capacity
If the temperature of a gas is constant, what happens to the pressure of a gas when the volume increases?
Boyle's law states gas at a constant temperature, increasing the volume of a gas causes a decrease in the pressure.
If the temperature of a gas is constant, what happens to the volume when the pressure increases?
Boyle's law states gas at a constant temperature, increasing the volume of a gas causes a decrease in the pressure.
Convert the mass values of each element into moles. Report your answers to at least two places after the decimal. C - 49.47 g H - 5.20 g N - 28.85 g O - 16.48 g
C - 4.12 mol H - 5.2 N - 2.06 O - 1.03 This is because the empirical formula is a representation of the relative number of atoms, or moles of atoms, of each element in a molecule. So, to find it, we'll need to convert these mass values into moles.
If we had 100 grams of the white powder, based on the percentages recovered, how many grams of each element would we have? C - 49.47 % H - 5.20 % N - 28.85 % O - 16.48 %
C - 49.47 H - 5.20 N - 28.85 O - 16.48
Based on this information, what would be the empirical formula of this substance?
C4H5N2O is the empirical formula of the substance but that doesn't mean we're done here. All the empirical formula tells us is that the ratio between C:H:N:O is 4:5:2:1. What you have to do now is find the molecular formula so we know how many atoms are in a molecule of this substance.
Glucose has the chemical formula C6H12O6. The empircical formula of glucose is_
CH2O
A compound is 24.7 % calcium, 1.2 % hydrogen, 14.8 % carbon and 59.3 % oxygen. Determine the chemical formula of the compound.
Ca(HCO₃)₂
If the pressure of a gas is constant, what happens to the volume when the temperature increases?
Charle's law states when pressure and number of molecules is constant when the tempurature increases, the volume will also increase
Use the diagram to the right to determine the correct order of events during this reaction:
Energy is absorbed to break bonds, then energy is released to form new bonds
Guy Lussac's law states that there is a ? relationship between the temperature and pressure of a gas. In other words, if the temperature of a gas increases, the pressure of that gas will ?. This law holds if the ? and number of molecules is kept constant.
direct increase volume