Q: Which of the following is the correct mole-to-particle conversion for $$2.5$$ moles of $$\mathrm{CO_2$}$$ molecules?

$$2.5 \times 6.022 \times 10$$^{23}$$ = 1.51 \times 10$$^{24}$$ molecules

Q: Which of the following is the correct calculation for percent yield?

$$\frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$$

Question 1

Which of the following is the correctly balanced equation for the reaction of calcium hydroxide with hydrochloric acid?

Accepted Answer

$$\mathrm{Ca(OH)_2 + 2HCl \rightarrow 2H_2O + $$CaCl_2$$}$$

Question 2

Potassium chlorate ($$\mathrm{$$KClO_3$$}) is $$heated strongly in a laboratory demonstration. What type of reaction occurs and what are the products?

Accepted Answer

Decomposition; $$\mathrm{$$KClO_3$$ \rightarrow KCl + O_2$}$$

Question 3

How many moles of nitrogen gas ($$\mathrm{N_2$}) $$are formed when $$4.56 	imes 10$$^{22}$$ molecules of ammonia ($$\mathrm{$$NH_3$$}$$) decompose according to 2$$\mathrm{$$NH_3$$ ightarrow $$N_2 + 3H_2$$}$$?

Accepted Answer

$$0.038$$ moles

Question 4

A student decomposes $$15.0$$ moles of hydrogen peroxide ($$\mathrm{H_2O_2}). $$How many grams of oxygen gas ($$\mathrm{O_2$}) $$are produced? (Molar mass of $$\mathrm{O_2$} is$$ $$32.00 g/$$mol)

Accepted Answer

$$240 g$$

Question 5

Given the reaction $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, if $$25.0 g of $$methane and $$80.0 g of $$oxygen are mixed, which is the limiting reactant?

Accepted Answer

Methane ($$\mathrm{CH_4$})$$

Question 6

In the reaction $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, what is the theoretical yield of $$\mathrm{CO_2$} (in $$grams) when $$25.0 g of $$methane is the limiting reactant? (Molar mass of $$\mathrm{CH_4$}$$: $$16.0 g/$$mol, $$\mathrm{CO_2$}$$: $$44.0 g/$$mol)

Accepted Answer

$$68.8 g$$

Question 7

If only $$60.0 g of$$ $$\mathrm{CO_2$} is $$produced from the reaction of $$25.0 g $$methane and $$80.0 g $$oxygen, what is the percent yield?

Accepted Answer

$$87.2\%$$

Question 8

A compound contains $$40.0\%$$ carbon, $$6.7\%$$ hydrogen, and $$53.3\%$$ oxygen by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 9

Which step is NOT required when determining the empirical formula from percent composition?

Accepted Answer

Multiply each mole value by Avogadro's number

Question 10

A $$25.00 mL $$sample of NaOH is titrated with $$0.200 M$$ $$\mathrm{H_2SO_4}$$, requiring $$18.75 mL of $$acid to reach equivalence. What is the molarity of the NaOH solution? (Use $$\mathrm{H_2SO_4 + 2NaOH \rightarrow Na_2SO_4 + 2H_2O})$$

Accepted Answer

$$0.300 M$$

Question 11

Which equation correctly relates the volumes and molarities in a titration involving $$\mathrm{H_2SO_4}$$ and NaOH, considering the stoichiometry?

Accepted Answer

$$2M_1V_1 = M_2V_2$$

Question 12

Which of the following is the correct mole-to-particle conversion for $$2.5$$ moles of $$\mathrm{CO_2$}$$ molecules?

Accepted Answer

$$2.5 	imes 6.022 	imes 10$$^{23}$$ = 1.51 	imes 10$$^{24}$$ molecules

Question 13

Which of the following best describes a limiting reactant in a chemical reaction?

Accepted Answer

The reactant that is completely consumed first, limiting the amount of product formed

Question 14

In a real-world scenario, why is percent yield often less than 100%?

Accepted Answer

Because some product may be lost during purification or side reactions may occur

Question 15

Which of the following is the correct balanced equation for the decomposition of hydrogen peroxide?

Accepted Answer

$$2\mathrm{H_2O_2 \rightarrow 2H_2O + O_2$}$$

Question 16

A solution contains $$0.500$$ moles of $$\mathrm{NaCl} in$$ $$250 mL of $$water. What is its molarity?

Accepted Answer

$$2.00 M$$

Question 17

Which of the following is a double replacement reaction?

Accepted Answer

$$\mathrm{$$AgNO_3$$ + NaCl \rightarrow AgCl + $$NaNO_3$$}$$

Question 18

Which of the following is the correct calculation for percent yield?

Accepted Answer

$$\frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100\%$$

CHEM 100 – Exam 3 Study Guide: Core Concepts and Practice Problems

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