Q: How many molecules are present in 10.0 grams of H$$_2S$$? (Molar mass of H$$_2S = 34.08 g/$$mol, Avogadro's number = $$6.022 \times 10$$^{23}$$ molecules/mol)

$$1.77 \times 10$$^{23}$$ molecules

Q: Which of the following is the correct molar mass conversion factor for methane (CH$$_4$$)?

$$\frac{1\ \text{mole CH}_4}{16.0\ \text{g CH}_4}$$

Q: A city burns $$2.13 \times 10^8$ grams of CH_4$ per day. How many grams of CO_2$ are produced? (Molar mass CH_4$ = 16.05 g/mol, CO_2$ = 44.01 g/mol, reaction: CH_4$ + 2O_2$ → CO_2$ + 2H_2$O)

$$5.84 \times 10^8$ grams CO_2$

Question 1

Which of the following statements best describes the relationship between mass, moles, and particles for a compound, as shown in the diagram?

Accepted Answer

Grams of a compound are converted to moles using the molar mass, and moles are converted to molecules using Avogadro's number.

Question 2

How many molecules are present in 10.0 grams of H$$_2S$$? (Molar mass of H$$_2S = 34.08 g/$$mol, Avogadro's number = $$6.022 	imes 10$$^{23}$$ molecules/mol)

Accepted Answer

$$1.77 	imes 10$$^{23}$$ molecules

Question 3

Which of the following is the correct molar mass conversion factor for methane (CH$$_4$$)?

Accepted Answer

$$\frac{1\ 	ext{mole CH}_4}{16.0\ 	ext{g CH}_4}$$

Question 4

A city burns $$2.13 	imes 10^8$ grams of CH_4$ per day. How many grams of CO_2$ are produced? (Molar mass CH_4$ = 16.05 g/mol, CO_2$ = 44.01 g/mol, reaction: CH_4$ + 2O_2$ → CO_2$ + 2H_2$O)

Accepted Answer

$$5.84 	imes 10^8$ grams CO_2$

Question 5

Which of the following best describes the Law of Conservation of Mass as illustrated in the reaction C(s) + O$$_2(g$$) → CO$$_2(g$$)?

Accepted Answer

The total number of atoms is the same before and after the reaction.

Question 6

Which of the following is a correct balanced equation for the combustion of propane (C$$_3H$_8$$)?

Accepted Answer

C$$_3H$_8 + 5O$_2$$ → 3CO$$_2 + 4H$_2O$$

Question 7

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

Accepted Answer

It loses electrons and is oxidized.

Question 8

In the reaction 2Na(s) + Cl$$_2(g$$) → 2NaCl(s), which element is oxidized and which is reduced?

Accepted Answer

Na is oxidized, Cl is reduced.

Question 9

Which of the following best explains why increasing temperature generally increases the rate of a chemical reaction?

Accepted Answer

Molecules move faster, leading to more frequent and energetic collisions.

Question 10

Which of the following is a characteristic of an endothermic reaction, as shown in the energy diagram?

Accepted Answer

The products have higher energy than the reactants.

Question 11

A chemist reacts 1.80 g of Na with excess water. How many grams of NaOH are produced? (Molar mass Na = 22.99 g/mol, NaOH = 40.00 g/mol, reaction: 2Na + 2H$$_2O$$ → 2NaOH + H$$_2)$$

Accepted Answer

3.13 g NaOH

Question 12

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

Accepted Answer

A solid melting into a liquid.

Question 13

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

Accepted Answer

It lowers the activation energy, increasing the reaction rate.

Question 14

Which of the following is the correct mole ratio between N$$_2$$ and NH$$_3 in $$the reaction N$$_2 + 3H$_2$$ → 2NH$$_3$$?

Accepted Answer

$$\frac{1\ 	ext{mol N}_2}{2\ 	ext{mol NH}_3}$$

Question 15

Which of the following is a double replacement reaction?

Accepted Answer

AgNO$$_3(aq) + $$NaCl(aq) → AgCl(s) + NaNO$$_3(aq)$$

Question 16

Which of the following best describes an effective collision in the context of chemical reactions?

Accepted Answer

A collision where molecules have proper orientation and sufficient energy to react.

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