4: Stoichiometry. Quantitative Information about Chemical Reactions

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Stoichiometry

Exercise \(\PageIndex{1}\)

The thermal decompostion of potassium chlorate results in the formation of potassium chloride and oxygen. How many grams of potassium chloride are formed when 2.45 g of potassium chlorate completely decomposed?

a. 0.89g

b. 2.45g

c. 1.49g

d. 0.097g

Answer: c. 1.49g

Exercise \(\PageIndex{1}\)

The thermal decompostion of potassium chlorate results in the formation of potassium chloride and oxygen. How many grams of oxygen are formed when 2.45 g of potassium chlorate is completely decomposed?

a. 0.98g

b. 2.45g

c. 0.87g

d. 0.960g

Answer: d. 0.960g

Exercise \(\PageIndex{1}\)

Magnesium hydroxide reacts with phosphoric acid to produce magnesium phosphate and water. What is the maxiumum quantity (in grams) of magnesium phosphate that can be produced if 2.00 g of magnesium hydroxide is added to 2.10g of phosphoric acid?

a. 2.81g

b. 3.67g

c. 2.0g

d. 2.10g

Answer: a. 2.81g

Exercise \(\PageIndex{1}\)

A student performs the reaction in question 3 and gets a yield of 2.67g. What is the percent yield of the students work?

a. 105%

b. 100%

c. 88.0%

d. 95.0%

Answer: d. 95.0%

Exercise \(\PageIndex{1}\)

How many grams of CaCl₂ can be formed from 150.g HCl? Assume excess CaO. The unbalanced reaction is

\(C a O+H C l \rightarrow C a C l_{2}+H_{2} O\)

a. 114g

b. 48.6g

c. 228g

d. NOTA

Answer: c. 228g

Exercise \(\PageIndex{1}\)

How many grams of Fe(NO₃)₃ can be formed from 75.9g Fe₂S₃? Assume excess HNO₃. The unbalanced reaction is

\(Fe_{2} S_{3}+H N O_{3} \rightarrow H_{2} S+Fe(NO_{3})_{3}\)

a. 331g

b. 44.2g

c. 177g

d. NOTA

Answer: c. 177g

Exercise \(\PageIndex{1}\)

How many grams of Na₂S can be formed from 115g NaCl? Assume excess Fe₂S₃. The unbalanced reaction is

\(Fe_{2} S_{3}+NaCl \rightarrow Na_{2} S+FeCl_{3}\)

a. 76.8g

b. 19.8g

c. 153.6g

d. NOTA

Answer: a. 76.8g

Exercise \(\PageIndex{1}\)

How many grams of Mg₃N₂ can be formed from 75.0g Mg(OH)₂? Assume excess NH₃. The unbalanced reaction is

\(Mg(OH)_{2}+NH_{3} \rightarrow MgN_{2} + H_{2}O\)

a. 14.4g

b. 43.3g

c. 129g

d. NOTA

Answer: b. 43.3g

Exercise \(\PageIndex{1}\)

How many grams of Ca₃(PO₄)₂ can be formed from 175g Ca(OH)₂? Assume excess H₃PO₄. The unbalanced reaction is

\(Ca(OH)_{2}+H_{3}PO_{4} \rightarrow Ca_{3}(PO_{4})_{2} + H_{2}O\)

a. 314g

b. 244g

c. 58.3g

d. NOTA

Answer: b. 244g

Exercise \(\PageIndex{1}\)

How many grams of CaO will react with 150.0g HCl? The unbalanced reaction is

\(CaO +HCl \rightarrow CaCl_{2} + H_{2}O\)

a. 194.9g

b. 115.4g

c. 150.0g

d. NOTA

Answer: b. 115.4g

Exercise \(\PageIndex{1}\)

What is the percent yield of CaCl₂ if 76.1g of CaCl₂ is formed for the reaction in question 1? The unbalanced reaction is

\(CaO +HCl \rightarrow CaCl_{2} + H_{2}O\)

a. 33.3%

b. 76.1%

c. 66.8%

d. NOTA

Answer: a. 33.3%

Exercise \(\PageIndex{1}\)

What is the percent yield of Fe(NO₃)₃ if 146g of Fe(NO₃)₃ is formed? The unbalanced reaction is

\(Fe_{2} S_{3}+H N O_{3} \rightarrow H_{2} S+Fe(NO_{3})_{3}\)

a. 82.5%

b. 41.3%

c. 74.2%

d. NOTA

Answer: a. 82.5%

Exercise \(\PageIndex{1}\)

What is the percent yield of Fe(NO₃)₃ if 146g of Fe(NO₃)₃ is formed? The unbalanced reaction is

\(Fe_{2} S_{3}+H N O_{3} \rightarrow H_{2} S+Fe(NO_{3})_{3}\)

a. 82.5%

b. 41.3%

c. 74.2%

d. NOTA

Answer: a. 82.5%

Exercise \(\PageIndex{1}\)

How many grams of H₃PO₄ will react with 175g of Ca(OH)₂? The unbalanced reaction is

\(Ca(OH)_{2}+H_{3}PO_{4} \rightarrow Ca_{3}(PO_{4})_{2} + H_{2}O\)

a. 51.3g

b. 154g

c. 347g

d. NOTA

Answer: b. 154g

Exercise \(\PageIndex{1}\)

What is the percent yield of Ca₃(PO₄)₂ if 93g of Ca₃(PO₄)₂ is formed? The unbalanced reaction is

\(Ca(OH)_{2}+H_{3}PO_{4} \rightarrow Ca_{3}(PO_{4})_{2} + H_{2}O\)

a. 98.6%

b. 76.2%

c. 38.1%

d. NOTA

Answer: c. 38.1%

Exercise \(\PageIndex{1}\)

How many grams of O₂ is present upon completion of a reaction with 67.0 grams of C and 194 grams of O₂. The unbalanced reaction is

\(C+O \rightarrow C O_{2}\)

a. 0.00g

b. 16.0g

c. 111g

d. NOTA

Answer: b. 16.0g

Exercise \(\PageIndex{1}\)

How many grams of O₂ is present upon completion of a reaction with 67.0 grams of C and 194 grams of O₂. The unbalanced reaction is

\(C+O \rightarrow C O_{2}\)

a. 0.00g

b. 13.0g

c. 27.0g

d. NOTA

Answer: a. 0.00g

Exercise \(\PageIndex{1}\)

If 212g CO₂ is produced from the reaction of 67.0 grams of C and 194 grams of O₂, what is the percent yield? The unbalanced reaction is

\(C+O \rightarrow C O_{2}\)

a. 86.2%

b. 43.1%

c. 64.2%

d. NOTA

Answer: a. 86.2%

Exercise \(\PageIndex{1}\)

If the percent yield of a reaction of 67.0 grams of C and 194 grams of O₂ was 92.1%, how much CO₂ is produced? The unbalanced reaction is

\(C+O \rightarrow C O_{2}\)

a. 212g

b. 246g

c. 227g

d. NOTA

Answer: c. 227g

Exercise \(\PageIndex{1}\)

How many grams of oxygen are present upon completion of the reaction of 120. grams of Al and 120. grams of O₂? The unbalanced reaction is

\(Al+O_{2} \rightarrow Al_{2} O_{3}\)

a. 120.g

b. 107g

c. 13.0g

d. NOTA

Answer: c. 13.0g

Exercise \(\PageIndex{1}\)

How much Al₂O₃ is formed from the reaction of 120. grams of Al and 120 grams of oxygen if the percent yield is 91.6%. The unbalanced reaction is

\(Al+O_{2} \rightarrow Al_{2} O_{3}\)

a. 193g

b. 207g

c. 226g

d. NOTA

Answer: b. 207g

Stoichiometry of Mg(s) and HCl(aq)

Exercise \(\PageIndex{1}\)

If 1.0 mol of Mg reacts with 3.0 mol of HCl, how many moles of gas will be produced?

a. 0.5mol

b. 1.0mol

c. 2.0mol

d. 3.0mol

Answer: b. 1.0mol

Exercise \(\PageIndex{1}\)

How many moles of gas will be produced from 2.43g of Mg?

a. 0.05mol

b. 0.08mol

c. 0.1mol

d. 2.0mol

Answer: c. 0.1mol

Exercise \(\PageIndex{1}\)

How many grams of gas will be formed if 0.243g of Mg is dissolved completely in the HCl solution?

a. 0.020g

b. 0.030g

c. 0.050g

d. 0.080g

Answer: a. 0.020g

Exercise \(\PageIndex{1}\)

How many moles of gas will be formed if it takes 20.0ml of 0.1M HCl to dissolve all the Mg?

a. 0.1mol

b. 0.01mol

c. 0.002mol

d. 0.001mol

Answer: c. 0.002mol

Exercise \(\PageIndex{1}\)

What is the volume of the gas at STP if 20.0ml of 0.1M HCl is used to dissolve all the Mg? (note, you need to cover gas laws before you can answer this).

a. 2.24L

b. 0.224L

c. 0.0224L

d. 0.0448L

Answer: d. 0.0448L

Limiting Reagents

Exercise \(\PageIndex{1}\)

How many grams of CO₂ can be formed from 67 grams of C and 194 grams of O₂? The unbalanced equation is

\(C+O_{2} \rightarrow CO_{2}\)

a. 250g

b. 270g

c. 44g

d. NOTA

Answer: a. 250g

Exercise \(\PageIndex{1}\)

How many grams of Fe₂S₃ can be formed from 780 grams of Na₂S and 324 grams of FeCl₃? The unbalanced equation is

\(Na_{2}S + FeCl_{3} \rightarrow Fe_{2}S_{3} + NaCl\)

a. 416g

b. 324g

c. 208g

d. NOTA

Answer: c. 208g

Exercise \(\PageIndex{1}\)

How many grams of Mg(OH)₂ can be formed from 165 grams of H₂O and 165 grams of Mg₃N₂? The unbalanced equation is

\(Mg_{3}N_{2} + H_{2}O \rightarrow Mg(OH)_{2} + NH_{3}\)

a. 165g

b. 268g

c. 495g

d. NOTA

Answer: b. 268g

Exercise \(\PageIndex{1}\)

How many grams of SO₂ can be formed from 45.0 grams of S and 60.0 grams of O₂? The unbalanced equation is

\(S+O_{2} \rightarrow SO_{2}\)

a. 89.7g

b. 120.5g

c. 60.0g

d. NOTA

Answer: a. 89.7g

Exercise \(\PageIndex{1}\)

How many grams of Al₂O₃ can be formed from 120. grams of Al and 120. grams of O₂? The unbalanced equation is

\(Al+O_{2} \rightarrow Al_{2} O_{3}\)

a. 255g

b. 226g

c. 240g

d. NOTA

Answer: b. 226g

Molarity Calculations

Exercise \(\PageIndex{1}\)

3.0g of a substance is dissolved in water. The volume of this solution is 40.0ml. What is the molarity of the solution? (The molecular weight of the substance is 63.4g/mol.)

a. 1.2M

b. 0.0012M

c. 2.8M

d. None of the above

Answer: a. 1.2M

Exercise \(\PageIndex{1}\)

A student is performing an experiment with 30.0ml of an unknown solution that has a molarity of 5.0M. How many moles are present in the unknown solution?

a. .091mol

b. 1.5mol

c. 0.15mol

d. None of the above

Answer: c. 0.15mol

Exercise \(\PageIndex{1}\)

2.5g of a substance is dissolved in water. The molarity of the solution is 3.0M. What is the volume of the solution? (The molecular weight of the substance is 102.4g/mol.)

a. 73ml

b. 8.1ml

c. 81ml

d. None of the above

Answer: b. 8.1ml

Exercise \(\PageIndex{1}\)

An unknown amount of an unknown is dissolved in water. The molarity of the solution is 3.0M. The volume of the solution 50.0ml. What is the mass of the substance? (The molecular weight of the substance is 21.6g/mol.)

a. 6.9g

b. 0.0069g

c. 3.2g

d. None of the above

Answer: c. 3.2g

Limiting Reagents and Stoichiometry

Exercise \(\PageIndex{1}\)

The molarity of Na₃PO₄ is 8.000x10^-2M, and the molarity of BaCl₂ is 1.000x10^-1M. If you start with 25.00ml of Na₃PO₄ and 25.00ml of BaCl₂, what is the limiting reagent?

a. BaCl₂

b. Na₃PO₄

c. NaCl₂

d. None of the above

Answer: a. BaCl₂

Exercise \(\PageIndex{1}\)

What is the mass of Ba₃(PO4)₂(s) after the reaction?(MW=601.93g/mol)

a. 0.5016g

b. 1.384x10^-6g

c. 0.1672g

d. None of the above

Answer: a. 0.5016g

Exercise \(\PageIndex{1}\)

What is the concentration of Na⁺ after the reaction?

a. 0.1000M

b. 0.1200M

c. 0.5000M

d. None of the above

Answer: b. 0.1200M

Exercise \(\PageIndex{1}\)

What is the concentration of Cl^- after the reaction?

a. 0.1200M

b. 0.1000M

c. 0.2000M

d. None of the above

Answer: b. 0.1000M

Exercise \(\PageIndex{1}\)

What is the concentration PO₄^-3 after the reaction?

a. 1.243M

b. 5.000M

c. 6.667x10^-3M

d. None of the above

Answer: c. 6.667x10^-3M

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