Q: How many molecules are present in 2.5 moles of CO$$_2$$?

$$2.5 \times 6.02 \times 10$$^{23}$$ = 1.505 \times 10$$^{24}$$ molecules

Q: A sample contains $$1.8 \times 10$$^{24}$$ atoms of sulfur (S). How many moles of S atoms are present?

$$1.8 \times 10$$^{24}$$ \div 6.02 \times 10$$^{23}$$ = 2.99$$ moles

Q: How many oxygen atoms are in $$0.150$$ mole of aspirin, C$$_9H$_8O$_4$$?

$$0.150 \text{ mol} \times 4 \text{ mol O} \times 6.02 \times 10$$^{23}$$ \text{ atoms/mol} = 3.61 \times 10$$^{23}$$ atoms

Q: What is the molar mass of lithium carbonate, Li$$_2CO$_3$$?

$$2 \times 6.94 + 12.01 + 3 \times 16.00 = 73.89 g/$$mol

Q: Which of the following reactions is a combustion reaction?

$$CH_4(g) + 2O_2(g$$) \rightarrow $$CO_2(g) + 2H_2O(g$$) + \text{energy}$$

Q: How many moles of Fe$$_2O$_3$$ can be formed from 6.0 moles of O$$_2 in $$the reaction $$4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$$?

$$6.0 \text{ mol O}_2 \times \frac{2 \text{ mol Fe}_2O_3}{3 \text{ mol O}_2} = 4.0$$ mol Fe$$_2O$_3$$

Question 1

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

Accepted Answer

Avogadro's number is the number of particles (atoms, molecules, or ions) in one mole of a substance.

Question 2

How many molecules are present in 2.5 moles of CO$$_2$$?

Accepted Answer

$$2.5 	imes 6.02 	imes 10$$^{23}$$ = 1.505 	imes 10$$^{24}$$ molecules

Question 3

A sample contains $$1.8 	imes 10$$^{24}$$ atoms of sulfur (S). How many moles of S atoms are present?

Accepted Answer

$$1.8 	imes 10$$^{24}$$ \div 6.02 	imes 10$$^{23}$$ = 2.99$$ moles

Question 4

How many oxygen atoms are in $$0.150$$ mole of aspirin, C$$_9H$_8O$_4$$?

Accepted Answer

$$0.150 	ext{ mol} 	imes 4 	ext{ mol O} 	imes 6.02 	imes 10$$^{23}$$ 	ext{ atoms/mol} = 3.61 	imes 10$$^{23}$$ atoms

Question 5

What is the molar mass of lithium carbonate, Li$$_2CO$_3$$?

Accepted Answer

$$2 	imes 6.94 + 12.01 + 3 	imes 16.00 = 73.89 g/$$mol

Question 6

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

$$59.8 \div 18.02 = 3.32$$ moles

Question 7

Which of the following is a balanced chemical equation?

Accepted Answer

$$2Al(s) + 3S(s) \rightarrow Al_2S_3(s)$$

Question 8

Which type of reaction is represented by the following equation? $$2Na(s) + Cl_2$(g) \rightarrow 2NaCl(s)$$

Accepted Answer

Combination reaction

Question 9

In the reaction $$2HgO(s) \rightarrow 2Hg(l) + O_2$(g)$$, what type of reaction is occurring?

Accepted Answer

Decomposition reaction

Question 10

Which of the following reactions is a combustion reaction?

Accepted Answer

$$CH_4(g) + 2O_2(g$$) ightarrow $$CO_2(g) + 2H_2O(g$$) + 	ext{energy}$$

Question 11

Which of the following is true about oxidation in a redox reaction?

Accepted Answer

Oxidation is the loss of electrons.

Question 12

In the reaction $$Sn(s) \rightarrow Sn$$^{4+}$$(aq) + 4e^-$$, what process is occurring?

Accepted Answer

Oxidation

Question 13

A reaction releases heat and the energy of the products is less than the energy of the reactants. What type of reaction is this?

Accepted Answer

Exothermic reaction

Question 14

Which factor will increase the rate of a chemical reaction?

Accepted Answer

Increasing the temperature

Question 15

How many moles of Fe$$_2O$_3$$ can be formed from 6.0 moles of O$$_2 in $$the reaction $$4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$$?

Accepted Answer

$$6.0 	ext{ mol O}_2 	imes \frac{2 	ext{ mol Fe}_2O_3}{3 	ext{ mol O}_2} = 4.0$$ mol Fe$$_2O$_3$$

Question 16

A reaction between H$$_2$$ and O$$_2$$ produces $$13.1 g of $$water. How many grams of O$$_2$$ reacted? (Molar mass H$$_2O$$ = $$18.02 g/$$mol, O$$_2$$ = $$32.00 g/$$mol, $$2H_2(g) + O_2$(g) \rightarrow 2H_2O(g))$$

Accepted Answer

$$13.1 	ext{ g H}_2O 	imes \frac{1 	ext{ mol H}_2O}{18.02 	ext{ g}} 	imes \frac{1 	ext{ mol O}_2}{2 	ext{ mol H}_2O} 	imes 32.00 	ext{ g O}_2 = 11.6 g O$_2$$

Question 17

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst lowers the energy of activation and increases the reaction rate without being consumed.

Question 18

Which of the following is a correct mole-mole ratio for the reaction $$3H_2(g) + N_2$(g) \rightarrow 2NH_3(g)$$ between H$$_2$$ and NH$$_3$$?

Accepted Answer

$$\frac{2 	ext{ mol NH}_3}{3 	ext{ mol H}_2}$$

Chemical Quantities and Reactions – General Chemistry Chapter 7 Study Notes

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