Chapter 12 Chemistry Study Guide

The decomposition of potassium chlorate yields oxygen gas. If the yield is 95%, how many grams of KClO₃ are needed to produce 10.0 L of O₂? 2KClO₃(s) 2KCl(s) + 3O₂(g)

10.0 L x 100%/95% =10.5L theoretical yield 10.5L O₂ x 1 mol O₂/22.4 L O₂ x 2 mol KClO₃/3 mol O₂ x 122.6 g KClO₃/1mol KClO₃ =38.4g KClO₃

If 8.00 mol of NH₃ reacted with 14.0 mol of O₂, how many moles of H₂O will be producded? 4NH₃ (g) + 7O₂ (g)→ 4NO₂ + 6H₂O (g)

12.0 mol of H₂O

For the reaction 2Na(s) + Cl₂(g) 2NaCl(s), how many grams of NaCl could be produced from 103.0g of Na and 13.0 L of Cl₂ (at STP)?

13.0 L Cl x 1 mol Cl₂/22.4 L Cl₂= 0.580 mol Cl₂ 103.0g Na x 1 mol Na/23g Na=4.48 mol Na Cl₂ is limiting reagent: 0.580 mol Cl₂ x 2 mol NaCl/1 mol Cl₂=1.16 mol NaCl 1.16 mol NaCl x 58 g NaCl/1 mol NaCl=67.3 g NaCl

If a total of 13.5 mol of NaHCO₃ and 4.5 mol of C₆H₈O₇react, how many moles of CO₂ and Na₃C₆H₅O₇ will be produced? 3NaHCO₃ (aq) + C₆H₈O₇ (aq)→ 3CO₂ (g) + 3H₂O(s) +Na₃C₆H₅O₇ (aq)

13.5 mol of CO₂ and 4.5 mol of Na₃C₆H₅O₇

Assuming STP and a stoichiometric amount of NH₃ and NO in an expandable container originally at 15 L, what is the final volume if the reaction goes to completion? 4NH₃ (g) + 6NO(g) → 5N₂ (g) + 6H₂O(g)

15 L of given reactants x 11 L of products/10 L of reactants = 16.5 L

What is the limiting reagent when 150.0g of nitrogen react with 32.1g of hydrogen? N₂(g) + 3H₂(g) → 2NH₃(g)

150.0g N₂ x 1 mol N₂/ 28g N₂=5.36 mol N₂ 32.1g H₂ x 1 mol H₂/2g H₂=16.1 mol H₂ 5.36 mol N₂/16.1 mol H₂= 1 mol N₂/3 mol H₂ There is no limiting reagent. The mole ratio of the reactants is exactly 1 mol N₂ to 3 mol H₂

How many grams of CO are needed to react with an excess of Fe O to produce 209.7g Fe? Fe₂O₃ (s) + 3CO(g) → 3CO₂(g) + 2Fe(s)

209.7g Fe x 1 mol Fe/55.85g Fe x 3 mol CO/2 mol Fe x 28.01g CO/1 mol CO = 157.8g CO

What is the mole ratio of D to A in the generic chemical reaction? 2A + B→C + 3D

3/2

If a tricycle factory ordered 33,432 wheels in 2002 and used all of them, how many tricycles did the factory produce?

33,432 wheels/ 3 wheels/tricycles= 11,114 tricycles

How many liters of O₂ are needed to react completely with 45.0 L of H₂S at STP? 2H₂S(g) + 3O₂(g) → 2SO₂(g) + 2H₂O(g)

45.0 L H₂S x 1 mol H₂S/22.4 L H₂S x 3 mol O₂/2 mol H₂S 22.4 L O₂ /1 mol O₂ = 67.5 L O₂

A 500g sample of Al₂(SO₄)₃ is reacted with 450g of Ca(OH)₂. A total of 596g of CaSO₄ is produced. What is the limiting reagent in this reaction, and how many moles of excess reagent are unreacted? Al₂(SO₄)₃ (aq) + 3Ca(OH)₃ (s) → 2Al(OH)₃ (s) + 3CaSO₄(s)

500g Al₂(SO₄)₃ x 1 mol Al₂(SO₄)₃/ 342g Al₂(SO₄)₃ x 3 mol Ca(OH)₂/ 1 mol Al₂(SO₄)₃ x 74g Ca(OH)₂/ 1 mol Ca(OH)₂= 325g Ca(OH)₂ 450g-325g=125g There are 125g excess Ca(OH)₂ Al(SO₄)₃ is the limiting reagent. 125g Ca(OH)₂ x 1 mol Ca(OH)₂/ 74g Ca(OH)₂=1.69 mol Ca(OH)₂ There are 1.69 mol Ca(OH)₂ remaining of unreacted excess reagent.

Consider the following reaction: 2H₂S(g) + 3O₂(g) 2SO₂(g) + 2H₂O(g) If O₂ was the excess reagent, 8.3 mol of H₂S were consumed, and 137.1g of water were collected after the reaction has gone to completion, what is the percent yield of the reaction?

8.3 mol H₂S x 2 mol H₂O/2 mol H₂S x 18g H₂O/1 mol= 149.4g H₂O theoretical yield percent yield=137.1g/149.4g x 100%=92%

If 8.6 L of H₂ reacted with 4.3 L of O₂ at STP, what is the volume of the gaseous water collected (assuming that none of it condenses)? 2H₂ (g) + O₂ (g)→ 2H₂O(g)

8.6 L H₂/ (22.4 L/1 mol) x 2 mol H₂O/2 mol H₂ x 22.4 L/ 1 mol = 8.6 L H O

Describe an experience you've had making or building something where the amount of each ingredient or building block came in fixed ratios.

A sample answer includes building a model airplane. For each model there will be two wings and three wheels. In order for the model to look correct or work properly, there must be a certain, unvarying number of wings and wheels

Calculate the number of moles of Al₂O₃ that are produced when 0.50 mol of Fe is produced in the following reaction. 2Al(s) + 3FeO(s) → 3Fe(s) + Al₂O₃(s) A. 0.20 mol B. 0.40 mol C. 0.60 mol D. 0.90 mol

A. 0.20 mol

Which conversion factor do you first to calculate the number of grams of CO₂ produced by the reaction of 50.6g of CH₄ with O₂? The equation for the complete combustion of methane is: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) A. 1 mol CH₄/16.0g CH₄ B. 2 mol O₂/ 1 mol CO₂ C. 16.0g CH₄/ 1 mol CO₄ D. 44.0g CO₂/ 2 mol CO₂

A. 1 mol CH₄/16.0g CH₄

At STP, how many liters of oxygen are required to react completely with 3.6 liters of hydrogen to form water? 2H₂(g) + O₂(g) → 2H₂O(g) A. 1.8 L B. 3.6 L C. 2.0 L D. 2.4 L

A. 1.8 L

How many grams of chromium are needed to react with an excess of CuSO₄ to produce 27.0g Cu? 2Cr(s) + 3CuSO₄(aq) → Cr₂(SO₄)₃ (aq) + 3Cu(s) A. 14.7g B. 18.0g C. 33.2g D. 81.5g

A. 14.7g

Methane and hydrogen sulfide form when hydrogen reacts with carbon disulfide. Identify the excess reagent and calculate how much remains after 36 L of H₂, reacts with 12 L if CS₂. 4H₂(g) + CS₂(g) → CH₄(g) + 2H₂S(g) A. 3 L CS₂ B. 6 L CS₂ C. 9 L CS₂ D. 12 L H₂

A. 3 L CS₂

Which of the following is true about the total number of reactants and the total number of products in the reaction shown below? C₅H₁₂(l) + 8O₂ → 5CO₂(g) + 6H₂O(g) A. 9 moles of reactants chemically change into 11 moles of product. B. 9 moles of reactants chemically change into 11 grams of product. C. 9 moles of reactants chemically change into 11 liters of product. D. 9 moles of reactants chemically change into 11 atoms of product.

A. 9 moles of reactants chemically change into 11 moles of product.

The calculation of quantities in chemical equations is called A. Stoichiometry B. Dimensional analysis C. Percent Composition D. Percent yield

A. Stoichiometry

Which statement is true if 12 mol CO and 12 mol Fe₂O₃ are allowed to react? 3CO(g) + Fe₂O₃(s) → 2Fe(s) + 3CO₂(g) A. The limiting reagent is CO and 8.0 mol Fe will be formed B. The limiting reagent is CO and 3.0 mol CO₂ will be formed C. The limiting reagent is Fe₂O₃ and 24 mol Fe will be formed D. The limiting reagent is Fe₂O₃ and 36 mol CO₂ will be formed

A. The limiting reagent is CO and 8.0 mol Fe will be formed

The amount of product formed when a reaction is carried out in the laboratory

Actual yield

Solid sodium reacts violently with water, producing heat, hydrogen gas, and sodium hydroxide. How many molecules of hydrogen gas are formed when 48.7g of sodium are added to water? 2Na + 2H₂O → 2NaOH + H₂

Assume the sodium is limiting: 48.7g Na x 1 mol Na/23.0g Na x 1 mol H₂/2 mol Na x (6.02 x 10²³ molecules H₂)/1 mol H₂ = 6.37 x 10²³ molecules H₂

How many liters of chlorine gas can be produced when 0.98 L of HCl react with excess O₂, at STP? 4HCl(g) + O₂ → 2Cl₂(g) + 2H₂O(g) A. 0.98 L B. 0.49 L C. 3,9 L D. 2.0 L

B. 0.49 L

How many moles of aluminum are needed to react completely with 1.2 mol of FeO? 2Al(s) + 3FeO(s) → 3Fe(s) + Al₂O₃(s) A. 1.2 mol B. 0.8 mol C. 1.6 mol D. 2.4 mol

B. 0.8 mol

Which of the following statements is true about the following reaction? 3NaHCO₃(aq) + C₆H₈O₇(aq) → 3CO₂(g) + 3H₂O(g) + Na₃C₆H₅O₇(aq) A 22.4 L of CO₂(g) are produced for every liter of C₆H₈O₇ B. 1 mole of water is produced for every mole of carbon dioxide produced C. 6.02 x 10²³ molecules of Na₃C₆H₅O₇(aq) are produced for every mole of NaHCO₃(aq) used D. 54g of water are produced for every mole of NaHCO₃(aq) are produced

B. 1 mole of water is produced for every mole of carbon dioxide produced

How many moles of H₃PO₄ are produced when 71.g P₄O₁₀ reacts completely to form H₃PO₄? P₄H₁₀(s) + 6H₂O(l) → 4H₂PO₄(aq) A 0.0635 mol B. 1.00 mol C. 4.00 mol D. 1.6.0 mol

B. 1.00 mol

How many moles of glucose C₆H₁₂O₆ can be "burned biologically when 10.0 mol of oxygen is available? C₆H₁₂O₆(s) + 6O₂(g) → 6CO₂(g) + 6H₂O(l) A. 0.938 mol B. 1.67 mol C. 53.3 mol D. 60.0 mol

B. 1.67 mol

When iron rusts in air, iron(III) oxide is produced. How many moles of oxygen react with 2.4 mol of iron in the rusting reaction? 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s) A. 1.2 mol B. 1.8 mol C. 2.4 mol D. 3.2 mol

B. 1.8 mol

Metallic copper is formed when aluminum with copper(II) sulfate. How many grams of metallic copper can be obtained when 54.0g of Al react with 319g of CuSO₄? Al + 3CuSO₄ → Al₂(SO₄)₃ + 3Cu A. 21.2g B. 127g C. 162g D. 381g

B. 127g

The equation below shows the decomposition of lead nitrate. How many grams of oxygen are produced when 11.5g NO₂ is formed? 2Pb(NO₃)₂ (s) → 2PbO(s) + 4NO₂(g) + O₂(g) A. 1.00g B. 2.00g C. 2.88g D. 32.0g

B. 2.00g

How many liters of NH₃ at STP, will react with 5.3g O₂ to form NO₂ and water? 4NH₃(g) + 7O₂(g) → 4NO₂ + 6H₂O(g) A. 0.00423 L B. 2.12 L C. 3.03 L D. 6.49 L

B. 2.12 L

How many liters of NH₃ are needed to react completely with 30.0 L of NO (at STP)? 4NH₃ (g) + 6NO(g) → 5N₂ (g) + 6H₂O(g) A. 5.0 L B. 20.0 L C. 7.5 L D. 120.0 L

B. 20.0 L

Iron(III) oxide is formed when iron combines with oxygen in the air. How many grams of Fe₂CO₃ are formed when 16.7g of Fe reacts completely with oxygen? 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s) A. 12.0g B. 23.9g C. 47.8g D. 95.6g

B. 23.9g

Aluminum reacts with sulfuric acid to produce aluminum sulfate and hydrogen gas. How many grams of aluminum sulfate would be formed if 250g H₂SO₄ completely reacted with aluminum? 2Al(s) + 3H₂SO₄(aq) → Al₂(SO₄)₃ (aq) + 3H₂(g) A. 0.85g B. 290g C. 450g D. 870g

B. 290g

Which of the following is an INCORRECT interpretation of the balanced equation shown below?2S(s) + 3O₂(g) → 2SO₃(g) A. 2 atoms S + 3 molecules O₂ → 2 molecules SO₃ B. 2g S + 3g O₂ → 2g SO₃ C. 2 mol S + 2 mol O₂ → 2 mol SO₃ D. None of the above

B. 2g S + 3g O₂ → 2g SO₃

Which of the following would be the limiting reagent in the reaction shown below? 2H₂(g) + O₂(g) → 2H₂O(g) A. 50 molecules of H₂ B. 50 molecules of O₂ C. Neither A nor B is limiting D. Both A and B are considered limiting reagents

B. 50 molecules of O₂

What is the maximum number of grams of PH₃ that can be formed when 6.2g of phosphorous reacts with 4.0g of hydrogen to from PH₃ P₄(g) + 6H₂(g) → 4PH₃(g) A. 0.43g B. 6.8g C. 270g D. 45g

B. 6.8g

Calcium oxide, or lime is produced by the thermal decomposition of limestone in the reacton CaCO₃(s) ∆→ CaO(s) + CO₂(g). What mass of lime can be produced from 1.5 x 10³kg of limestone? A. 8.4 x 10⁵ B. 8.4 x 10² C. 8.4 kg D. None of the above

B. 8.4 x 10²

The first step in most stoichiometry problems is to _______ A. Add the coefficients of the reagents B. Convert given quantities to moles C. Convert given quantities to volumes D. Convert given quantities to masses

B. Convert given quantities to moles

When two substances react to form products, the reactant which is used up is called the _____ A. Determining reagent B. Limiting reagent C. Excess reagent D. Catalytic reagent

B. Limiting reagent

Identify the limiting reagent and the volume of CO₂, formed when 11 L CS₂, reacts with 18 L O₂, gas and SO₂, gas at STP CS₂(g) +3O₂(g) → CO₂(g) + 2SO₂(g) A. CS₂; 5.5 L CO₂ B. O₂; 6.0 L CO₂ C. CS₂; 11 L CO₂ D. O₂; 27 L CO₂

B. O₂; 6.0 L CO₂

When 0.1 mol of calcium reacts with 880g of water, 22.4 L if hydrogen gas from (at STP). How would the amount of hydrogen produced if the volume of water was decreased to 440mL (440g) A. Only one half the volume of hydrogen would be produced B. The volume of hydrogen produced would be the same C. The volume of hydrogen produced would double D. No hydrogen would be produced

B. The volume of hydrogen produced would be the same

Mercury can be obtained by reacting mercury(III) sulfide with calcium oxide. How many grams of calcium oxide are needed to produce 36.0g of Hg? 4HgS(l) + 4CaO(s) → 4Hg(l)+ 3CaSO₄(s) + CaSO₄ A. 1.80g B. 7.56g C. 10.1g D. 13.4g

C. 10.1g

How many grams of beryllium are needed to produce 36.0g of hydrogen (Assume an excess of water) Be(s) + 2H₂O → Be(OH)₂ (aq) + H₂(g) A. 4.00g B. 36.0g C. 162g D. 324g

C. 162g

In the reaction 2CO(g) + O₂(g) → 2CO₂, what is the ratio of moles of oxygen used to moles of CO₂, produced? A. 1:1 B. 2:1 C. 1:2 D. 2:2

C. 1:2

If 1 egg and 1/3 cup of oil are needed for each bag of brownie mix, how many bags of brownie mix do you need if you use up all 3 eggs and 1 cup of oil? A. 1 B. 2 C. 3 D. 4

C. 3

In a particular reaction between copper metal and silver nitrate, 12.7g Cu produced 38.1g Ag. What is the percent yield of silver in this reaction? Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag A. 56.7% B. 77.3% C. 88.2% D. 176%

C. 88.2%

In a chemical reaction, the mass of the products _______. A. Is less than the mass of the reactants B. Is greater than the mass of the reactants C. Is equal to the mass of the reactants D. Has no relationship to the mass of the reactants

C. Is equal to the mass of the reactants

In every chemical reaction, _____. A. Mass and molecules are conserved B. Moles and liters are conserved C. Mass and atoms are conserved D. Moles and molecules are conserved

C. Mass and atoms are conserved

What is conserved in the reaction shown below? N₂(g) + 3F₂(g) → 2NF₃(g) A. Atoms only B. Mass only C. Mass and atoms only D. Moles only

C. Mass and atoms only

In any chemical reaction, the quantities that are preserved are ____. A. The number of moles and volumes B. The number of molecules and the volumes C. Mass and number of atoms D. Mass and moles

C. Mass and number of atoms

When an equation is used to calculate the amount of product that will form during a reaction, then the value obtained is called the _____. A. Actual yield B. Percent yield C. Theoretical yield D. Minimum yield

C. Theoretical yield

How many liters of hydrogen gas are needed to react with CS₂ to produce 2.50 L of CH₄ at STP? 4H₂(g) + CS₂(l) → CH₄(g) + 2H₂S(g) A. 2.50 L B. 5.00 L C. 7.50 L D. 10.0 L

D. 10.0 L

Hydrogen gas can be produced by reacting aluminum with sulfuric acid. How many moles of sulfuric acid are needed to completely react with 15..0 mol of aluminum? 2Al(s) + 3H₂SO₄(aq) → Al₂(SO₄)₃ (aq) + 3H₂(g) A. 0.100 mol B. 10.0 mol C. 15.0 mol D. 22.5 mol

D. 22.5 mol

Hydrogen gas is produced when zinc reacts with hydrochloric acid. If the actual yield of this reaction is 85%, how many grams of zinc are needed to produce 112 L of H₂ at STP? Zn(s) + 2HCl(aq) → ZnCl₂ + H₂(g) A. 95g B. 180g C. 280g D. 380g

D. 380g

How many grams of H₃PO₄ are produced when 10.0 moles of water reacts with an excess of P₄H₁₀? P₄H₁₀(s) + 6H₂O(l) → 4H₂PO₄(aq) A. 1.22g B. 6.7g C. 147g D. 653g

D. 653g

When glucose is consumed, it reacts with oxygen in the body to produce carbon dioxide, water, and energy. How many grams of carbon dioxide would be produced if 45g of C₆H₁₂O₆ completely reacted with oxygen? A. 1.5g B. 1.8g C. 11g D. 66g

D. 66g

Lead nitrate can be decomposed by heating. What is the percent yield of the decomposition if 9.9g Pb(NO₃)₂ are heated to give 5.5g of PbO? 2Pb(NO₃)₂ (s) → 2PbO(s) + 4NO₂(g) + O₂(g) A. 44% B. 56% C. 67% D. 82%

D. 82%

Glucose C₆H₁₂O₆ is a good source of food energy, When it reacts with oxygen, carbon dioxide, and water are formed. How many liters of CO₂ are produced when 126g of glucose completely react with oxygen? C₆H₁₂O₆(s) + 6O₂(g) → 6CO₂(g) + 6H₂O(l) + 673 kcal A. 4.21 L B. 5.33 L C. 15.7 L D. 94.1 L

D. 94.1 L

Which of the following is NOT a reason why actual yield is less than theoretical yield? A. Impure reactants present B. Competing side reactions C. Loss if product during purification D. Conservation of mass

D. Conservation of mass

What is conserved in the reaction shown below? H₂(g) + Cl₂(g) → 2HCl(g) A. Mass only B. Mass and moles only C. Mass, moles. and molecules only D. Mass, moles, molecules and volume

D. Mass, moles, molecules and volume

Which of the following is NOT true about "yield"? A. The value of the actual yield must be given in order for the percent yield to be calculated B. The percent yield is the ratio of the actual yield to the theoretical yield C. The actual yield may be different from the theoretical yield because reactions do not always go to completion D. The actual yield may be different from the theoretical yield because insufficient limiting reagent was used

D. The actual yield may be different from the theoretical yield because insufficient limiting reagent was used

Which of the following is NOT true about limiting and excess reagents? A. The amount of product obtained is determined by the limiting reagent B. A balanced equation is necessary to determine which reactant is the limiting reagent C. Some of the excess reagent is left over after the reaction is complete D. The reactant that has the smallest given mass is the limiting reagent

D. The reactant that has the smallest given mass is the limiting reagent

Which type of stoichiometric calculation does not require the use of the molar mass? A. Mass-mass problems B. Mass-volume problems C. Mass-particle problems D. Volume-volume problems

D. Volume-volume problems

The reactant that is not completely used in a reaction

Excess Reagent

The reactant that determines the amount of product that can be formed in a reaction

Limiting reagent

When a mixture of sulfur and metallic silver is heated, silver sulfide is produced. What mass of silver sulfide is produced from a mixture of 3.0g of Ag and 3.0g of S₈? 16Ag(s) + S₈(s) → 8Ag₂S(s)

Limiting reagent is silver: 3.0g x 1 mol Ag/108g Ag= 0.03 mol Ag 3.0g S₈ x 1 mol S₈/256g S₈= 0.01 mol S₈ 0.03 mol Ag x 8 mol Ag₂/ 16 mol x 248g Ag₂S/ 1 mol Ag₂S= Ag₂S 3.72g of silver sulfide is produced

This is conserved in every ordinary chemical reaction

Mass

A chemical problem may be presented to you in units of moles, mass, or volume. Which one of these can be directly used in your arithmetic no matter what the conditions are?

Moles can be directly used. The number of molecules or moles is the basic unit in solving chemical problems. When the number of moles are known, the mass and volume can be determined.

Assuming no errors were made in measuring the yield, can the percent yield of a chemical reaction be greater than 100%?

No, percent yield is actual yields/ theoretical yields .x 100%. The theoretical yield is the maximum amount of product that could be formed from given amounts of products. The actual yield must be less than or equal to the theoretical yield.

This quantity can always be used in the same ways as moles when interpreting balanced chemical equations

Number of molecules

The ration of the actual yield to the theoretical yield

Percent yield

What is the general procedure for solving a stoichiometric problem?

The coefficients from the balanced equation are used to write mole ratios. The mole ratios relate the moles of reactants by the mole ratio, you can determine the number of moles of the product.

What is the importance of the coefficients in a balanced chemical reaction?

The coefficients in a balanced chemical equation indicate the relative number of moles of reactants and products. From this information, the amounts of reactants and products can be calculated. The number of moles may be converted to mass, volume, or number of representative particles.

The maximum that determines of product that could be formed from given amounts of reactants

Theoretical yield

If 5.0 g of H₂ are reacted with excess CO, how many grams of CH₃OH are produced, based on a yield of 86%? CO(g) + 2H₂(g) → CH₃OH(l)

Theoretical yield: 5.0g H₂ x 1 mol H₂/2.0g H₂ x 1 mol CH₃OH/2 mol H₂ x 32g CH₃OH/1 mol CH₃OH= 40g CH₃OH 40g CH OH x 86% = 34g CH₃OH

This is conserved only in reactions where the temperature is constant and the number of moles of gaseous reactants is the same as that of gaseous products

Volume

In which kind of stoichiometric calculation can the steps involving conversion to and from moles to be omitted? Explain why it is possible to do so.

Volume-Volume conversion between gases do not require mole conversions. Molar volumes of all gases at STP are the same. The coefficients in a balanced equation indicate the relative number of moles and the relative volumes of interacting gases