Q: How many molecules are present in $$0.75$$ moles of $$CO_2$$? Use Avogadro’s number $$6.02 \times 10$$^{23}$$.

$$4.52 \times 10$$^{23}$$ molecules

Q: A patient is prescribed $$0.200$$ mole of aspirin ($$C_9H_8O_4). $$How many oxygen atoms are in this dose?

$$4.82 \times 10$$^{24}$$ atoms

Q: Which conversion factor would you use to convert from grams of $$C_6H_{12}O_6$ to molecules of C_6H$$_{12}$$O_6$$?

$$\frac{1\ \text{mole}}{180.16\ \text{g}}$$ then $$\frac{6.02 \times 10$$^{23}$$\ \text{molecules}}{1\ \text{mole}}$$

Question 1

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

Accepted Answer

It is the number of particles (atoms, molecules, or ions) in 1 mole of a substance.

Question 2

How many molecules are present in $$0.75$$ moles of $$CO_2$$? Use Avogadro’s number $$6.02 	imes 10$$^{23}$$.

Accepted Answer

$$4.52 	imes 10$$^{23}$$ molecules

Question 3

A patient is prescribed $$0.200$$ mole of aspirin ($$C_9H_8O_4). $$How many oxygen atoms are in this dose?

Accepted Answer

$$4.82 	imes 10$$^{24}$$ 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 $$500 g of$$ $$NaCl. $$How many moles of $$NaCl$$ are present? (Molar mass of $$NaCl = 58.44 g/$$mol)

Accepted Answer

$$8.56$$ moles

Question 6

Which of the following is NOT evidence of a chemical reaction?

Accepted Answer

A liquid evaporates when heated.

Question 7

Balance the following equation: $$C_2H_6 + O_2$ \rightarrow CO_2$ + H_2O$$

Accepted Answer

$$2C_2H_6 + 7O_2 \rightarrow 4CO_2 + 6H_2O$$

Question 8

How many grams of silver ($$Ag) $$are in $$3.00$$ moles? (Molar mass of $$Ag = 107.9 g/$$mol)

Accepted Answer

$$323.7 g$$

Question 9

A sample contains $$1.20 	imes 10$$^{24}$$ atoms of sulfur (S$). How many moles of S$ are present?

Accepted Answer

$$2.00$$ moles

Question 10

Which of the following best explains why the coefficients in a balanced chemical equation must be the lowest possible ratio?

Accepted Answer

To reflect the conservation of mass and atoms in a chemical reaction.

Question 11

A patient with bipolar disorder is prescribed $$0.050$$ moles of lithium carbonate ($$Li_2CO_3). $$What is the mass of this dose? (Molar mass $$= 73.89 g/$$mol)

Accepted Answer

$$14.8 g$$

Question 12

Which conversion factor would you use to convert from grams of $$C_6H_{12}O_6$ to molecules of C_6H$$_{12}$$O_6$$?

Accepted Answer

$$\frac{1\ 	ext{mole}}{180.16\ 	ext{g}}$$ then $$\frac{6.02 	imes 10$$^{23}$$\ 	ext{molecules}}{1\ 	ext{mole}}$$

Question 13

Which of the following best describes the role of subscripts in a chemical formula?

Accepted Answer

They show the number of atoms of each element in one molecule and the number of moles of each element in one mole of compound.

Question 14

A chemical equation is balanced when:

Accepted Answer

The number of atoms of each element is the same on both sides of the equation.

Question 15

Which of the following is the correct balanced equation for the reaction of aluminum with sulfur to form aluminum sulfide ($$Al_2S_3$$)?

Accepted Answer

$$2Al + 3S \rightarrow Al_2S_3$$

Question 16

A sample of water has a mass of $$36.0$$ grams. How many moles of water are present? (Molar mass $$H_2O = 18.02 g/$$mol)

Accepted Answer

$$2.00$$ moles

Question 17

Which of the following best describes the physical state symbol $$(aq) in a $$chemical equation?

Accepted Answer

The substance is dissolved in water.

Question 18

If $$2.0$$ moles of $$Al$$ react completely, how many atoms of $$Al$$ are involved? (Avogadro’s number $$= 6.02 	imes 10$$^{23}$$)

Accepted Answer

$$1.20 	imes 10$$^{24}$$ atoms

Chemical Quantities and Reactions: Study Notes

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