Q: How many molecules are present in $$0.250$$ mole of $$CO_2$$?

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

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

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

Q: Methane ($$CH_4) $$has a molar mass of $$16.04\ g/mol. $$How many molecules are present in $$32.08$$ grams of methane?

$$1.20 \times 10$$^{24}$$ molecules

Question 1

Which of the following best describes a combination (synthesis) reaction?

Accepted Answer

Two or more elements or compounds combine to form a single product.

Question 2

Given the balanced equation $$2Al(s) + 3S(s) \rightarrow Al_2S_3(s)$$, how many moles of sulfur are required to react completely with 4 moles of aluminum?

Accepted Answer

$$6$$ moles

Question 3

Which observation is NOT typically evidence of a chemical reaction?

Accepted Answer

Change in state from solid to liquid without any other change

Question 4

In the reaction $$Zn(s) + 2HCl(aq) \rightarrow $$ZnCl_2$$(aq) + H_2$(g)$$, which species is oxidized?

Accepted Answer

Zn

Question 5

How many molecules are present in $$0.250$$ mole of $$CO_2$$?

Accepted Answer

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

Question 6

Aspirin has the formula $$C_9H_8O_4. $$How many moles of oxygen atoms are present in $$0.200$$ mole of aspirin?

Accepted Answer

$$0.800$$ moles

Question 7

What is the molar mass of $$Li_2CO_3 ($$lithium carbonate)?

Accepted Answer

$$73.89\ g/mol$$

Question 8

How many moles of $$NaCl$$ are present in $$117$$ grams of $$NaCl$$? (Molar mass of $$NaCl = 58.44\ g/mol)$$

Accepted Answer

$$2.00$$ moles

Question 9

Which law states that mass is conserved in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 10

In the reaction $$2Ag(s) + S(s) \rightarrow Ag_2S(s)$$, if you start with $$215.8$$ grams of silver and $$32.07$$ grams of sulfur, what is the mass of $$Ag_2S$$ produced?

Accepted Answer

$$247.87$$ grams

Question 11

If $$6.0$$ moles of $$O_2$$ react with excess $$Fe$$ according to $$4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$$, how many moles of $$Fe_2O_3$$ are produced?

Accepted Answer

$$4.0$$ moles

Question 12

Which of the following is the correct mole ratio between $$Fe$$ and $$O_2 in $$the reaction $$4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$$?

Accepted Answer

$$4$$ moles $$Fe$$ : $$3$$ moles $$O_2$$

Question 13

A student mixes $$32.0$$ grams of $$N_2$$ with excess $$H_2 in $$the reaction $$N_2(g) + 3H_2(g$$) \rightarrow 2NH_3(g)$$. What mass of NH_3$ can be produced? (M$$_{$$N_2$$} = 28.02\ g/mol$$, M$$_{$$NH_3$$} = 17.04\ g/mol$$)

Accepted Answer

$$38.9$$ grams

Question 14

In a reaction, $$3.00$$ moles of $$CO$$ and $$5.00$$ moles of $$H_2$$ are mixed to produce $$CH_3OH$$ via $$CO(g) + 2H_2(g) \rightarrow CH_3OH(g). $$What is the limiting reactant?

Accepted Answer

$$H_2$$

Question 15

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

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

Question 16

Which statement about oxidation-reduction (redox) reactions is correct?

Accepted Answer

Oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 17

Methane ($$CH_4) $$has a molar mass of $$16.04\ g/mol. $$How many molecules are present in $$32.08$$ grams of methane?

Accepted Answer

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

Question 18

Which type of reaction is represented by $$2HgO(s) \rightarrow 2Hg(l) + O_2$(g)$$?

Accepted Answer

Decomposition

Question 19

A reaction produces $$5.00$$ grams of product, but the theoretical yield is $$6.50$$ grams. What is the percent yield?

Accepted Answer

$$76.9\%$$

Chemical Reactions and Quantities: Study Notes for Introductory Chemistry

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