CH. 8 Quantities in Chemical Reactions

What is the theoretical yield of a reaction if 25.0 grams of product were actually produced from a reaction that has a 88% yield?

28.4

Given that 4 NH3 + 5 O2 → 4 NO + 6 H2O, when 4.50 mol of H2O are formed, the amount of NO formed is:

3.00 mol.

A chemist wishes to perform the following reaction: N2 + 3 H2 → 2 NH3 If only 14.0 g of N2 is available, what is the minimum amount, in grams, of H2 needed to completely react with this quantity of N2?

3.03 g

How many moles of sodium metal are needed to make 3.6 moles of sodium chloride? Given the reaction: 2Na + Cl2 → 2NaCl A) 0.9

3.6

A sample of 8.5 g NH3 on oxidation produces 4.5 g of NO. Calculate the percent yield. Reaction: 4 NH3 + 5 O2 → 4 NO + 6 H2O

30%

If the theoretical yield of a reaction is 42.0 grams of product and the percent yield is 75%. How many grams were actually produced?

32

How many grams of NO2 are theoretically produced if we start with 1.20 moles of S and 9.90 moles of HNO ? 3 Reaction: S + 6HNO3 → H2SO4 + 6NO2 + 2H2O

331

How many grams of calcium phosphate are theoretically produced if we start with 3.40 moles of Ca(NO3)2 and 2.40 moles of Li3PO4? Reaction: 3Ca(NO3)2 + 2Li3PO4 → 6LiNO3 + Ca3(PO4)2

351

How many grams of water are made from the reaction of 4.0 grams of hydrogen gas? Given the reaction: 2H2 + O2 → 2H2O

36

Diatomic N2 can react with diatomic H2 to form ammonia (NH3). The balanced chemical equation is: If 6 moles of H2 totally reacted with more than enough N2, how many moles of ammonia would be expected to form?

4 Moles

Diatomic O2 can react with the element magnesium to form magnesium oxide (MgO). The balanced chemical equation is: If 4 moles of magnesium totally reacted with more than enough O2, how many moles of MgO would be expected to form?

4.4

How many moles of H2 can be made from complete reaction of 3.0 moles Al? Given: 2 Al + 6 HCl → 2 AlCl3 + 3 H2

4.5 Moles

Given that 4 NH3 + 5 O2 → 4 NO + 6 H2O, if 3.00 mol NH3 were made to react with excess of oxygen gas, the amount of H2O formed would be:

4.50 mol.

How many grams of water are theoretically produced for the following reaction given we have 2.6 moles of HCl and 1.4 moles of Ca(OH)2? Reaction: 2HCl + Ca(OH)2 → 2H2O + CaCl2

46.8

The theoretical yield of a reaction is 75.0 grams of product and the actual yield is 42.0g. What is the percent yield?

56.0

Determine the theoretical yield of C when 3 units of A and 10 units of B are reacted in the following generic chemical equation: 2A + 5B → 4C.

6

How many moles of lithium nitrate are theoretically produced if we start with 3.4 moles of Ca(NO3)2 and 2.4 moles of Li3PO4? Reaction: 3Ca(NO3)2 + 2Li3PO4 → 6LiNO3 + Ca3(PO4)2

6.8

How many grams of chlorine gas are needed to make 117 grams of sodium chloride? Given the reaction: 2Na + Cl2 → 2NaCl

71.0

What is the theoretical yield of waffles if you have 6 cups of flour, 9 eggs and 2 tbs of oil? Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles

8

If 16.0 grams of aluminum oxide were actually produced, what is the percent yield of the reaction below given that you start with 10.0 g of Al and 19.0 grams of O2? Reaction: 4Al + 3O2 → 2Al2O3

84.7%

How many eggs are needed to make 1 dozen waffles, assuming you have enough of all other ingredients? Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles

9

Iron metal reacts with oxygen to produce iron(III) oxide. If you have 12.0 moles of iron for complete reaction, you need:

9.0 moles of O2 and produce 6.0 moles of Fe2O3.

Which of the below statements about global warming is FALSE?

If the level of greenhouse gases increases, the temperature will decrease.

What is the excess reactant for the following reaction given we have 3.4 moles of Ca(NO3)2 and 2.4 moles of Li3PO4? Reaction: 3Ca(NO3)2 + 2Li3PO4 → 6LiNO3 + Ca3(PO4)2

Li3PO4

Which ingredient is the limiting reactant if you have 5 cups of flour, 9 eggs and 3 tbs of oil? Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles

flour

Consider the following reaction: 2 Mg + O2 → 2 MgO △H rxn = -1203 kJ Calculate the amount of heat (in kJ) associated with complete reaction of 4 moles of Mg.

-2406 kJ

Consider the following equation: CO + 2 H2 → CH3OH △H rxn = -128 kJ Calculate the amount of heat (in kJ) associated with complete reaction of 8.08 g H2.

-256 kJ

How many moles of NH3 can be produced by the reaction of 2.00 g of N2 with 3.00 g H2? Reaction: N2(g) + 3 H2(g) → 2 NH3(g)

0.143

How many moles of aluminum oxide are produced according to the reaction below given that you start with 10.0 grams of Al and 19.0 grams of O2? Reaction: 4Al + 3O2 → 2Al2O3

0.185

How many moles of chlorine gas are needed to make 0.6 moles of sodium chloride? Given the reaction: 2Na + Cl2 → 2NaCl

0.3

How many grams of water are made from the reaction of 16.0 grams of oxygen gas? Given the reaction: 2H2 + O2 → 2H2O

18

How many grams of aluminum oxide are produced according to the reaction below given that you start with 10.0 grams of Al and 19.0 grams of O2? Reaction: 4Al + 3O2 → 2Al2O3

18.9

Given the balanced equation CH4 + 2 O2 → CO2 + 2 H2O, which of the following is NOT a correct conversion factor?

2 mole H2O = 18.02 g

Consider the reaction: 2 Al + 3Br2 → 2 AlBr3 Suppose a reaction vessel initially contains 5.0 mole Al and 6.0 mole Br2. What is in the reaction vessel once the reaction has occurred to the fullest extent possible?

1.0 mole Al; 0 mole Br2; 4.0 mole AlBr3

How many moles of calcium chloride are theoretically produced for the following reaction given we have 2.6 moles of HCl and 1.4 moles of Ca(OH)2? Reaction: 2HCl + Ca(OH)2 → 2H2O + CaCl2

1.3

How many moles of water are made from complete reaction of 2.2 moles of oxygen gas with hydrogen gas? Given the reaction: 2H2 + O2 → 2H2O

1.4

What is the theoretical yield of waffles if you have 5 cups of flour, 9 eggs and 3 tbs of oil? Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles

10

How many grams of the excess reactant are left over according to the reaction below given that you start with 10.0 g of Al and 19.0 grams of O2? Reaction: 4Al + 3O2 → 2Al2O3

10.1

How many grams of sodium metal are needed to make 29.3 grams of sodium chloride? Given the reaction: 2Na + Cl2 → 2NaCl

11.5

How many moles of aluminum are needed to make 9 moles of molecular hydrogen? GIVEN the reaction: 2 Al + 6 HCl → 2 AlCl

12 Moles

Suppose two chemical reactions are linked together in a way that the O2 produced in the first reaction goes on to react completely with Mg to form MgO in the second reaction. Reaction one: 2 KClO3 → 3 O2 + 2 KCl Reaction two: 2 Mg + O2 → 2 MgO If you start with 4 moles of KClO3, how many moles of MgO could eventually form?

12 Moles

A 24.0 g sample of nitrogen gas reacts with an excess of hydrogen gas to give an actual yield of NH3. What is the percent yield for this reaction? Reaction: N2(g) + 3 H2(g) → 2 NH3(g)

13.2%

The reaction for the oxidation of NH3 is given as: 4 NH3 + 5 O2 → 4 NO + 6 H2O Under certain conditions the reaction will proceed at 29.8% yield of NO. How many grams of NH3 must be made to react with excess oxygen to yield 70.5 g of NO?

134

How many waffles can be made from 1 dozen eggs, assuming you have enough of all other ingredients? Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles

16

What is the limiting reactant for the reaction below given that you start with 10.0 grams of Al and 19.0 grams of O2? Reaction: 4Al + 3O2 → 2Al2O3

Al

The reaction of one mole of nitrogen gas with three moles of hydrogen gas releases 92 kJ of thermal energy to the surroundings. Which of the following is TRUE?

All of the above are true.

What is the limiting reactant for the following reaction given we have 3.4 moles of Ca(NO3)2 and 2.4 moles of Li3PO4? Reaction: 3Ca(NO3)2 + 2Li3PO4 → 6LiNO3 + Ca3(PO4)2

Ca(NO3)2

What is the excess reactant for the following reaction given we have 2.6 moles of HCl and Reaction: 2HCl + Ca(OH)2 → 2H2O + CaCl2

Ca(OH)2

Which is the limiting reactant in the following reaction given that you start with of Na2S and CuSO4? Reaction: Na2S + CuSO4 → Na2SO4 + CuS

CuSO4

For the following reaction you have 8 grams of hydrogen and 2 grams of oxygen.

False

For the following reaction you have 8 grams of hydrogen and 2 grams of oxygen. 2H2 + O2 → 2H2O The excess reactant is the oxygen.

False

Given the chemical equation: 2 Ca + O2 → 2 CaO, if 2 moles of CaO are formed in this reaction, then 2 moles of O2 must have reacted.

False

Given the reaction: 2 Na(s) + Cl2(g) → 2 NaCl(s) The conversion factor for chlorine gas to sodium metal is: 2 2 mol Cl ≡ 2 mol Na

False

Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins If you have 5 cups of flour, 3 eggs and plenty of blueberries, the limiting reactant is the eggs.

False

Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins. You can make 9 muffins from 3.5 cups of flour.

False

Greenhouse gases affect the temperature of the earth by blocking sunlight from reaching earth.

False

If it takes 2 cups of milk and 1 cup of cocoa mix to make three servings of hot chocolate, and you only have 1 cup of each, then you cannot make any hot chocolate.

False

If the theoretical yield of a reaction is 144 grams and the actual yield of the reaction is 72 grams, the percent yield of the reaction is 200%.

False

One of the advantages of burning fossil fuels is that it produces O2 for humans to breathe.

False

The enthalpy of reaction, △H rxn, is the amount of thermal energy that flows when a reaction occurs at constant temperature.

False

The limiting reactant determines what the actual yield is.

False

The limiting reactant is the product that is completely consumed in a chemical reaction.

False

The limiting reactant is the reactant that produces the maximum amount of product.

False

The primary source for the rising carbon dioxide levels is respiration of the Earth's growing population.

False

The theoretical yield is the amount of each reactant needed in order to make the maximum amount of product.

False

Which is the excess reactant in the following reaction given that you start with 15.5 g of Na2S and CuSO4? Reaction: Na2S + CuSO4 → Na2SO4 + CuS

Na2S

A balanced chemical equation used to prepare ammonium carbonate, (NH4)2CO3 , is: Which choice of reactant quantities shown below would result in the greatest amount of ammonium carbonate being formed?

React 4 moles NH3 , 2 moles CO2 , and 2 moles H2O

What is the limiting reactant for the reaction below given that you start with 2.50 grams C and 2.50 grams SiO2? Reaction: C + SiO2 → SiC + O2

SiO2

The average global temperature depends on all factors EXCEPT what?

The angle of the earth's surface in relation to the incoming sunlight

The primary cause of increasing greenhouse gases is:

The increased use of natural gas, petroleum and coal.

Which of the following statements is FALSE?

The percent yield = × 100%.

Consider the following generic chemical equation: 2A + 5B → C + 3D If you react 4 units of A with 10 units of B, which statement is TRUE?

There is just enough of A and B so that everything reacts completely.

An exothermic reaction has a negative enthalpy of reaction.

True

Before determining conversion factors, it is necessary to make sure the equation is properly balanced.

True

For the following reaction you have 8 grams of hydrogen and 2 grams of oxygen. 2H2 + O2 → 2H2O The limiting reagent is the oxygen.

True

Given the following generic equation, 2 A + 3B → A2B3 △H rxn = +444 kJ, if you completely reacted 1 mole of compound A, the amount of heat absorbed would be 222 kJ.

True

Given the reaction: 2 Na(s) + Cl2(g) → 2 NaCl(s) The conversion factor for chlorine gas to sodium chloride is: 1 mol Cl2 ≡ 2 mol NaCl

True

Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins If you have 9 cups of flour, 4 eggs and plenty of blueberries, the theoretical yield of muffins is 16.

True

Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins. You can make 1 dozen muffins from 3 eggs.

True

Global warming is due to the greenhouse gases preventing heat from Earth escaping into space.

True

Since heat must be supplied to melt ice, the melting of ice is an endothermic process and so has a positive enthalpy value.

True

Stoichiometry is a chemist's version of following a recipe.

True

The actual yield is the amount of product actually produced by a chemical reaction.

True

The actual yield is the same as the theoretical yield if the reaction goes to completion and there is no loss of product.

True

The conversion factor between mass and moles for a compound is the molar mass.

True

The conversion factor for moles of carbon dioxide to mass of carbon dioxide is: 1 mole CO2 ≡ 44.01 g.

True

The limiting reactant is not necessarily the reactant with the least mass.

True

The percent yield can never be greater than 100%.

True

The percent yield is calculated by dividing the actual yield by the theoretical yield times 100.

True

The primary greenhouse gas is carbon dioxide.

True

Thermal energy flows into the reaction and out of the surroundings in an endothermic reaction.

True

When viewing a chemical equation, the limiting reactant can never be a chemical on the product side of the equation.

True

Consider the following generic chemical equation: 2W + 3X → 3Y + Z When 5 units of W and 6 units of X are allowed to react, the limiting reactant would be:

X

Given the balanced equation CO2 + Si → SiO2 + C, if you were to react 1 mole of CO2 with 1 mole of Si, which statement is TRUE?

You have equal stoichiometric amounts of reactants

A tricycle factory uses the following items to produce one tricycle: 3 tires, 1 frame, and 2 pedals. If the factory has available 270 tires, 90 frames, and 170 pedals, which item would limit the amount of complete tricycles that can be assembled?

pedals

In order to determine the limiting reactant in a particular reaction, one must know each of the following EXCEPT:

the mass of each product formed.

Many metals react with halogens to give metal halides. For example, 2 Al (s) + 3 Cl2(g) → 2 AlCl3 (s) If you begin with 13.5 g of aluminum: A chemist wishes to perform the following reaction: N2 + 3 H2 → 2 NH3 If only 14.0 g of N2 is available, what is the minimum amount, in grams, of H2 needed to completely react with this quantity of N2?

you will need 53.2 g Cl2 for complete reaction and will produce 66.7 g of AlCl3