Q: Which of the following statements best describes a mole in chemistry?

A mole is a defined quantity equal to $$6.02 \times 10$$^{23}$$ particles.

Q: How many hydrogen atoms are present in 1 mole of aspirin ($$\mathrm{C_9H_8O_4}$$)?

$$8 \times 6.02 \times 10$$^{23}$$ atoms

Question 1

Which of the following statements best describes a mole in chemistry?

Accepted Answer

A mole is a defined quantity equal to $$6.02 	imes 10$$^{23}$$ particles.

Question 2

How many hydrogen atoms are present in 1 mole of aspirin ($$\mathrm{C_9H_8O_4}$$)?

Accepted Answer

$$8 	imes 6.02 	imes 10$$^{23}$$ atoms

Question 3

Which of the following is the correct balanced equation for the combustion of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

$$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$

Question 4

A reaction in which two or more reactants combine to form a single product is called:

Accepted Answer

Combination

Question 5

Which of the following is an example of a single replacement reaction?

Accepted Answer

$$\mathrm{Zn(s) + 2HCl(aq) \rightarrow H_2$(g) + $$ZnCl_2$$(aq)}$$

Question 6

What is the molar mass of $$\mathrm{K_2Cr_2O_7} ($$potassium dichromate)? (K = 39.1, Cr = 52.0, O = 16.0)

Accepted Answer

$$294.2\ \mathrm{g/mol}$$

Question 7

Which of the following best describes an oxidation reaction?

Accepted Answer

A reaction in which an atom loses electrons

Question 8

If $$54.6\ \mathrm{g} of$$ $$\mathrm{C_2H_2}$$ reacts with excess $$\mathrm{O_2$}$$, how many grams of $$\mathrm{CO_2$}$$ are produced? (Molar mass $$\mathrm{C_2H_2} = 26.04\ \mathrm{g/mol}$$, $$\mathrm{CO_2$} = 44.01\ \mathrm{g/mol}$$, reaction: $$2\mathrm{C_2H_2} + 5\mathrm{O_2$} \rightarrow 4\mathrm{CO_2$} + 2\mathrm{H_2O})$$

Accepted Answer

$$185\ \mathrm{g}$$

Question 9

Which of the following is true for a double replacement reaction?

Accepted Answer

Two compounds exchange ions to form two new compounds

Question 10

Which of the following is the correct mole-mole factor for the reaction $$2\mathrm{Ag} + \mathrm{S} \rightarrow \mathrm{Ag_2S}$$?

Accepted Answer

$$\frac{2\ \mathrm{mol\ Ag}}{1\ \mathrm{mol\ S}}$$

Question 11

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction that releases heat to the surroundings

Question 12

In the reaction $$2\mathrm{HgO} \rightarrow 2\mathrm{Hg} + \mathrm{O_2$}$$, what type of reaction is this?

Accepted Answer

Decomposition

Question 13

Which of the following is reduced in the reaction $$2\mathrm{Mg} + \mathrm{O_2$} \rightarrow 2\mathrm{MgO}$$?

Accepted Answer

O$$_2$$

Question 14

A student mixes solutions of $$\mathrm{Na_2SO_4}$$ and $$\mathrm{$$BaCl_2$$}$$ and observes a white precipitate. What type of reaction has occurred?

Accepted Answer

Double replacement

Question 15

Which of the following is the correct sequence for converting grams of a compound to molecules?

Accepted Answer

Grams $$\rightarrow$$ Moles $$\rightarrow$$ Molecules

Question 16

Which of the following is a correct example of a combination reaction?

Accepted Answer

$$\mathrm{2Fe + 3S \rightarrow Fe_2S_3}$$

Question 17

Which of the following statements about reaction rates is correct?

Accepted Answer

A catalyst decreases the activation energy of a reaction.

Question 18

In the reaction $$\mathrm{$$CuSO_4$$(aq) + Zn(s) \rightarrow $$ZnSO_4$$(aq) + Cu(s)}$$, which species is oxidized?

Accepted Answer

Zn

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