Unit 2: Reactions and Stoichiometry Practice Problems

What is the oxidation state of hydrogen in the following compound? NaH

-1

What is the oxidation state of nitrogen in the following molecule? N2H4

-2

Copper(I) iodide (CuI) is often added to table salt as a dietary source of iodine. How many moles of CuI are contained in 1.00 lb (454 g) of table salt containing 0.0100% CuI by mass?

.00024 mol

You find the mass of a sample of sodium chloride with an electronic balance is 1.22 g. What is this amount in moles?

.02

A 32.3 g sample of a CuCl2 solution contains 45.0 mg of CuCl2. What is the mass percent of the CuCl2?

.14%

If 3.35 L of a 0.450 M H3PO4 solution is to be diluted to a volume of 8.00 L, what is the concentration of the resulting solution?

.188 M

Dry ice is solid CO2. You place a piece of dry ice on a balance and find that its mass is 16.7 g. How many mol of CO2 are in the sample?

.379 mol

How many moles of N2 would be produced from a reaction between 0.851 mol H2O2 and an excess amount of N2H4, according to the following reaction. N2H4+2H2O2→N2+4H2O

.426 mol N2

How many moles of hydrogen will be needed to produce 0.36 mol of ammonia, according to the equation below? N2+3H2→2NH3

.54 mol H2

What is the concentration in M of a 1.25 L solution containing 0.750 mol of BaCl2?

.600 M

Calculate the molarity of 6.52 g of CoCl2 (129.8 g/mol) dissolved in an aqueous solution with a total volume of 75.0 mL.

.670 M

325 mL of a 2.25 M barium nitrate solution is mixed with an excess amount of potassium sulfate according to the following equation. Ba(NO3)2(aq)+K2SO4(aq)→BaSO4(s)+2KNO3(aq) How many moles of barium nitrate are available for the reaction?

.731 mol

What is the oxidation state of carbon in the following compound? C6H12O6

0

What is the oxidation state of sulfur in the following molecule? S8

0

Use the following reaction and equation for the next two problems. Iron(III) oxide reacts with carbon monoxide according to the equation below. Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g) If 3.5×1022 molecules of CO2 are produced, how many moles of Fe2O3 reacted?

0.019molFe2O3

An aqueous salt (NaCl) solution has a concentration of 0.225 M. How many mol of sodium chloride are in 170.0 mL of this solution?

0.0382 mol

The mass of a sample of Ca(OH)2 is 6.2 g. How many moles in this amount of substance?

0.084 mol

0.0062 mol of lead(II) nitrate is dissolved in 50.0 mL of water. What is the molarity of the solution?

0.124 M

150.0 mL of a 0.650 M Na2CO3 solution is diluted to 250.0 mL. What is the molarity of the diluted solution?

0.390 M

Iron(III) oxide reacts with carbon monoxide according to the equation below. Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g) If 0.25 mol of Fe2O3 react, how many mol of Fe will be produced?

0.50molFe

A sample of N2H4 contains 6.38×1020 molecules. How many moles is the sample?

1.06×10-3 mol N2H4

A cough syrup contains 5.00% ethyl alcohol, C2H5OH, by mass. If the density of the solution is 0.9928 g/mL, determine the molarity of the alcohol in the cough syrup.

1.077 M

Methane, CH4, is a greenhouse gas. How many hydrogen atoms are contained in 0.96 g of CH4?

1.4e23

A liter of air contains 9.2×1023 atoms of argon. How many moles of argon is this?

1.5 mol

Wine is approximately 12% ethanol (CH3CH2OH) by volume. Ethanol has a molar mass of 46.06 g/mol and a density 0.789 g/mL. How many moles of ethanol are present in a 750−mL bottle of wine?

1.5 mol

23.8 g of CH4 is added to 1.75 mol Cl2 . According the the reaction below. CH4(g)+2Cl2(g)→CH2Cl2(g)+2HCl(g) What is the maximum amount of HCl that can be produced by the 1.75 mol Cl2?

1.75 mol

Calculate the number of water molecules produced in the reaction below if 0.158 mol of methane (CH4) reacts with an excess amount of oxygen. CH4+2O2→2H2O+CO2

1.90×1023 molecules H2O

Baking soda is the chemical compound sodium bicarbonate, NaHCO3. The mass of baking soda that you use in a recipe is 0.26 g. How many formula units of NaHCO3 are in this amount?

1.9×1021 fm. un.

Cytosine is another of the bases that make up the DNA molecule. The chemical formula for cytosine is C4H5N3O. What is the formula mass of cytosine? (Use atomic masses to 2 decimal places and round your final answer to 2 decimal places.)

111.12

What volume of a 0.420 M C12H22O11 solution can be diluted to prepare 150.0 mL of a solution with a concentration of 0.0350 M?

12.5 mL

A bottle of a tile cleanser contains 135 g of HCl and 775 g of water. What is the percent by mass of HCl in this cleanser?

14.8%

What volume of a 3.00 M solution of glucose, C6H12O6, is required to prepare 250.00 mL of a 1.75 M glucose solution?

146 mL

Guanine is one of the four bases found in DNA. It has a chemical formula of C5H5N5O. What is the formula mass of guanine? (Use atomic masses to 2 decimal places and round your final answer to 2 decimal places.)

151.15

325 mL of a 2.25 M barium nitrate solution is mixed with an excess amount of potassium sulfate according to the following equation. Ba(NO3)2(aq)+K2SO4(aq)→BaSO4(s)+2KNO3(aq) What mass of precipitate will be formed?

171gBaSO4

Calculate the formula mass of C6H12O6

180.18

Calculate the percent of phosphorus in Ca3(PO4)2. (Round answers to the tenths place.)

19.97

Which of the following represents the balanced equation for the following reaction? Solid potassium chlorate decomposes to form solid potassium chloride and diatomic oxygen gas.

2 KClO3 → 2 KCl + 3 O2

How many grams of CO are needed to react with an excess of Fe2O3 to produce 2.79 g Fe? Fe2O3+3CO→3CO2+2Fe

2.10 g CO

What mass of NaCl is needed to make 150.0 mL of a 0.250 M solution?

2.19 g

What mass of iron(II) phosphate will be produced if 2.05 g of sodium phosphate is reacted with an excess amount of iron(II) chloride according to the reactions below? 3FeCl2+2Na3PO4→Fe3(PO4)2+6NaCl

2.24gFe3(PO4)2

Aqueous solutions of iron(III) nitrate and sodium hydroxide are mixed to form the precipitate iron(III) hydroxide. If 125 mL of 0.65 M NaOH is mixed with an excess amount of Fe(NO3)3 solution, what mass of Fe(OH)3 will be produced? Fe(NO3)3+3NaOH→3NaNO3+Fe(OH)3

2.9 g Fe(OH) 3

23.8 g of CH4 is added to 1.75 mol Cl2 . According the the reaction below. CH4(g)+2Cl2(g)→CH2Cl2(g)+2HCl(g) What is the maximum amount of HCl that can be produced by the 23.8 g CH4?

2.97 mol

A sample of aluminum sulfate, (Al2(SO4)3), contains 4.82×1022 formula units. What is the mass of this sample in grams?

27.4 g

How many grams of CO2 will be produced if 9.28 g of butane (C4H10) reacts with an excess amount of oxygen in a combustion reaction? 2C4H10+13O2→8CO2+10H2O

28.1gCO2

What volume of concentrated HCl solution contains 125 g of HCl? "Concentrated" hydrochloric acid is an aqueous solution of 37.2% HCl and has a density of 1.19 g/mL.

282 mL

Which of the following equations represents the reaction that takes place when aqueous solutions of chromium(III) sulfate and ammonium carbonate are mixed?

2Cr3+(aq)+3CO2−3(aq)→Cr2(CO3)3(s)

Which of the following is the balanced complete ionic equation for the molecular equation below? 2NaCl(aq)+2H2O(l)→2NaOH(aq)+H2(g)+Cl2(g)

2Na+(aq)+2Cl−(aq)+2H2O(l)→2Na+(aq)+2OH−(aq)+H2(g)+Cl2(g)

What is the oxidation state of carbon in the following polyatomic ion? C2O4 (2−)

3

A laboratory experiment calls for 0.125 M HNO3. What volume of 0.125 M HNO3 can be prepared from 0.250 L of 1.88 M HNO3?

3.76 L

Elemental silicon is used in computer microchips because of its semi-conductive property. What is the mass of 7.31×1024 atoms of Si?

341 g

Calculate the formula mass of Fe2(C2O4)3

375.76

What is the oxidation state of sulfur in the following compound? Na2SO3

4

Iron(III) oxide reacts with carbon monoxide according the reaction below. How many moles of iron will be formed if 478 g of iron(III) oxide reacts with an excess amount of carbon monoxide. Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g)

5.99molFe

Calculate the formula mass of Mg(OH)2

58.33

What is the oxidation state of chromium in the following polyatomic ion? Cr2O7 (2−)

6

If 5.50×1024 molecules of H2 react according to the equation below, how many moles of ammonia will be produced? 3H2+N2→2NH3

6.09 mol NH3

Sucrose, C12H22O11, is ordinary table sugar. How many carbon atoms are in 3.15 g of sucrose?

6.65×1022 atoms C

An average brewed cup (8 oz. or 237 mL) of coffee contains 150 mg of caffeine. What is the concentration of the caffeine in an average cup of coffee expressed in ppm? (Assume the density is 1.0 g/mL)

632

What is the mass of 0.486 mol of K2CO3?

67.2 g

To three significant digits, what is the mass percentage of iron in the compound Fe2O3?

69.9

How many molecules are in 52.8 g of CO2?

7.22e23

When potassium iodide and lead (II) nitrate react, a double replacement reaction occurs. Determine the mass of lead (II) iodide that will be produced if 3.28 mol of potassium iodide are used. 2KI+Pb(NO3)2→PbI2+2KNO3

756 g PbI2

Calculate the atomic mass of Ga2(Cr2O7)3. (Use atomic masses to 2 decimal places and round your final answer to 2 decimal places.)

787.44

Vitamin C is a covalent compound with the molecular formula C6H8O6. The recommended daily dietary allowance of vitamin C for children aged 4-8 years is 1.42×10−4 mol. How many molecules are in this amount of vitamin C?

8.55×1019 molecules C6H8O6

Calculate the percent of nitrate ion in Mg(NO3)2. (Round answers to the tenths place.)

83.6

It is suggested that manganese concentration in drinking water be no more than 0.050 ppm. What is this concentration in molarity? Assume a density of 1.0 g/mL. Express answer in M.

9.1e-7

A 50.0−g sample of industrial wastewater was determined to contain 0.48 mg of mercury. Express the mercury concentration of the wastewater in ppm.

9.6

A 23.2 g sample of a compound containing only carbon and hydrogen is found to have 21.4 g of C. Calculate the percent composition of the compound. (Round answers to the tenths place.)

92.2%C 7.8%H

An experiment in a general chemistry laboratory calls for a 1.50 M solution of HCl. How many mL of 11.9 M HCl would be required to make 750.0 mL of 1.50 M HCl?

94.5 mL

A 50.0−g sample of industrial wastewater was determined to contain 0.48 mg of mercury. Express the mercury concentration of the wastewater in ppb.

9600

What is the difference between a strong and weak acid?

A strong acid completely dissociates when dissolved in water and a weak acid only slightly dissociates.

Copper undergoes oxidation when placed in a solution of silver nitrate. If 6.2 g of copper is placed into 50.0 mL of a 2.5 M AgNO3 solution, which is the limiting reactant? Cu(s)+2AgNO3(aq)→Cu(NO3)2(aq)+2Ag(s)

AgNO3

Which of the following equations represents the reaction that takes place when aqueous solutions of aluminum nitrate and barium hydroxide are mixed?

Al3+(aq)+3OH−(aq)→Al(OH)3(s)

A 38.5 g sample of a compound that contains only arsenic and oxygen contains 25.10 g As and 13.40 g O. What is the empirical formula of this compound?

As2O5

For the following equation, write the complete ionic equation on your own paper, identify the spectator ions and then choose the correct net ionic equation from the choices below.Ba(NO3)2(aq)+Na2CO3(aq)→BaCO3(s)+2NaNO3(aq)

Ba2+(aq)+CO2−3(aq)→BaCO3(s)

Ethanol (grain alcohol), C2H5OH, is highly flammable. Which of the following reactions represents the combustion of ethanol?

C2H5OH(l)+3O2(g)→2CO2(g)+3H2O(l)

A sample of a molecular compound was analyzed and found to contain 36.35% of carbon, 6.07% of hydrogen and 57.58% of fluorine. Determine molecular formula of the compound if the molar mass of the compound is 99.0 g/mol.

C3H6F3

A 6.5 g sample of a compound contains 3.90 g C, 0.871 g H, and 1.73 g O. What is the empirical formula of this compound?

C3H8O

A compound with a percent composition of 49.47% C, 5.201% H, 28.84% N, and 16.48% O has a molecular mass of 194.2 amu. What is the compound's empirical formula? Write the elements in the formula in the same order as they are given here. What is the EMPIRICAL molar mass of this compound? What is the molecular formula for this compound?

C4H5N2O 97.11 C8H10N4O2

The empirical formula of a compound is CH. If the molar mass of this compound is experimentally determined to be 78.10 g, what is the molecular formula?

C6H6

What is the empirical formula of a compound containing 40.0% C, 6.71% H, and 53.28% O?

CH2O

What is the concentration of Al3+ and SO42− in a 0.750 M Al2(SO4)3 solution?

Concentration Al3+= 1.5M Concentration SO42−= 2.25M

Which of the following equations represents the reaction that takes place when aqueous solutions of copper(II) sulfate and sodium bromide are mixed?

CuSO4(aq)+NaBr(aq)→noreaction

Which of the following equations represents the reaction that takes place when aqueous solutions of potassium hydroxide and iron(III) nitrate are mixed?

Fe3+(aq)+3OH−(aq)→Fe(OH)3(s)

Write the complete ionic equation for the following molecular equation on your own paper. Once you have the complete ionic equation, identify the spectator ions. K2C2O4(aq)+Ba(OH)2(aq)⟶2KOH(aq)+BaC2O4(s)

K+(aq)andOH−(aq)

Which of the following equations represents the reaction that takes place when aqueous solutions of ammonium hydroxide and strontium acetate are mixed?

NH4OH(aq)+Sr(C2H3O2)2(aq)→noreaction

ethanol, C2H6O

Nonelectrolyte

In the following equation, determine which element is oxidized and which is reduced. (Enter the element name or symbol.) 2Al+3CoSO4→Al2(SO4)3+3Co

Oxidized- Aluminum Reduced- Co

In the following equation, determine which element is oxidized and which is reduced. (Enter the element name or symbol.) N2+3H2→2NH3

Oxidized- Hydrogen Reduced- Nitrogen

In the following equation, determine which element is the oxidizing agent and which is reducing agent . (Enter the element name or symbol.) 2PbS+3O2→2PbO+2SO2

Oxidizing Agent- Oxygen Reducing Agent- Sulfur

A 15.00 g sample of a compound is found to have 6.546 g P and 8.454 g O and a molar mass of 283.9 g/mol. What is the molecular formula of this compound?

P4O10

H2SO4

Strong Electrolyte

HBr

Strong Electrolyte

K2CO3

Strong Electrolyte

Which of the following statements is true of the chemical equation below? 2Fe+3Cl2→2FeCl3

There are 2 atoms of iron represented on the reactant and product sides of the equation.

Which of the following statements is true of the chemical equation below? Cu(s)+2AgNO3(aq)→2Ag(s)+Cu(NO3)2(aq)

There are 2 atoms of silver represented on the product side of the equation.

For the following equation, write the complete ionic equation on your own paper, identify the spectator ions and then choose the correct net ionic equation from the choices below. Zn(s)+2AgNO3(aq)→Zn(NO3)2(aq)+2Ag(s)

Zn(s)+2Ag+(aq)→Zn2+(aq)+2Ag(s)

The mass in grams of one mole of any element is numerically equal to its

atomic mass

The mass in grams of one mole of any compound is numerically equal to its

formula mass

An acid is a substance...

that forms H3O+ ions when dissolved in water.