Q: A sample contains $$0.250$$ moles of $$CO_2. $$How many $$CO_2$$ molecules are present in the sample?

$$1.51 \times 10$$^{23}$$ molecules

Q: How many atoms of oxygen are in $$0.200$$ moles of aspirin ($$C_9H_8O_4$$)?

$$4.82 \times 10$$^{23}$$ atoms

Q: How many atoms are in $$1.5$$ moles of aluminum ($$Al$$)?

$$9.03 \times 10$$^{23}$$ atoms

Question 1

Which of the following statements best describes Avogadro's number?

Accepted Answer

It is the number of particles in 1 mole of a substance, specifically $$6.02 	imes 10$$^{23}$$.

Question 2

A sample contains $$0.250$$ moles of $$CO_2. $$How many $$CO_2$$ molecules are present in the sample?

Accepted Answer

$$1.51 	imes 10$$^{23}$$ molecules

Question 3

How many atoms of oxygen are in $$0.200$$ moles of aspirin ($$C_9H_8O_4$$)?

Accepted Answer

$$4.82 	imes 10$$^{23}$$ atoms

Question 4

What is the molar mass of lithium carbonate ($$Li_2CO_3$$)? (Atomic masses: Li = 6.94, C = 12.01, O = 16.00)

Accepted Answer

$$73.89 g/$$mol

Question 5

A box contains $$737$$ grams of NaCl. How many moles of NaCl are present? (Molar mass of NaCl = $$58.44 g/$$mol)

Accepted Answer

$$12.6$$ moles

Question 6

Which of the following best illustrates the law of conservation of mass in a chemical reaction?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 7

In the reaction $$2Fe(s) + 3S(s) \rightarrow Fe_2S_3(s)$$, what is the mole ratio of $$Fe to$$ $$S$$?

Accepted Answer

$$2:3$$

Question 8

How many moles of $$Fe_2O_3$$ can be formed from $$9.0$$ moles of $$O_2 in $$the reaction $$4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$$?

Accepted Answer

$$6.0$$ moles

Question 9

A sample of water has a mass of $$59.8$$ grams. How many moles of water are in the sample? (Molar mass of $$H_2O = 18.02 g/$$mol)

Accepted Answer

$$3.32$$ moles

Question 10

In a reaction, $$3.00$$ moles of $$CO$$ and $$5.00$$ moles of $$H_2$$ are mixed to produce methanol ($$CH_4O) $$according to $$CO + 2H_2 \rightarrow CH_4O. $$What is the limiting reactant and how many moles of $$CH_4O$$ can be produced?

Accepted Answer

$$H_2 is $$limiting; $$2.50$$ moles of $$CH_4O$$ can be produced.

Question 11

If $$70.0$$ grams of $$SiO_2 ($$molar mass $$60.09 g/$$mol) and $$50.0$$ grams of $$C ($$molar mass $$12.01 g/$$mol) react according to $$SiO_2 + 3C$$ \rightarrow SiC + 2CO$$, which reactant is limiting?

Accepted Answer

$$SiO_2 is $$the limiting reactant.

Question 12

A reaction has a theoretical yield of $$100$$ grams but only $$85$$ grams of product are actually obtained. What is the percent yield?

Accepted Answer

$$85\%$$

Question 13

How many atoms are in $$1.5$$ moles of aluminum ($$Al$$)?

Accepted Answer

$$9.03 	imes 10$$^{23}$$ atoms

Question 14

Which of the following is NOT a correct conversion factor for $$1$$ mole of $$C_9H_8O_4 ($$aspirin)?

Accepted Answer

$$1$$ mole $$C_9H_8O_4 / 9$$ moles $$C$$

Question 15

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

Accepted Answer

It is the reactant that is used up first and limits the amount of product formed.

Question 16

A chemical reaction produces $$72.8$$ grams of $$LiHCO_3$$ from $$50.0$$ grams of $$LiOH. If $$the theoretical yield is $$85.0$$ grams, what is the percent yield?

Accepted Answer

$$85.6\%$$

Question 17

Which of the following is the correct molar mass for $$C_2H_6O ($$ethanol)? (Atomic masses: C = 12.01, H = 1.008, O = 16.00)

Accepted Answer

$$46.07 g/$$mol

Question 18

If $$32.0$$ grams of $$N_2 ($$molar mass $$28.02 g/$$mol) react completely to form $$NH_3$$ according to $$N_2 + 3H_2$$ \rightarrow 2NH_3$$, what mass of NH_3$ (molar mass 17.03$ g/mol) is produced?

Accepted Answer

$$38.9$$ grams

The Mole, Molar Mass, and Stoichiometry in Chemical Reactions

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