Question 1

Which of the following best explains why sodium (Na) tends to form a +1 ion in chemical reactions?

Accepted Answer

Sodium has one valence electron, which it loses to achieve a stable noble gas configuration.

Question 2

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

Accepted Answer

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

Question 3

Why do elements in the same group of the periodic table often form similar chemical reactions?

Accepted Answer

They have the same number of valence electrons.

Question 4

Which of the following statements about ionic bonds is correct?

Accepted Answer

Ionic bonds form when there is a large difference in electronegativity between two atoms.

Question 5

What is the correct set of coefficients to balance the following equation: $$\mathrm{Na + Pb(NO_3$)_2 \rightarrow $$NaNO_3$$ + Pb}$$?

Accepted Answer

$$\mathrm{2, 1, 2, 1}$$

Question 6

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of valence electrons between two nonmetals.

Question 7

How many moles of $$\mathrm{NaCl}$$ are present in 58.5 grams of $$\mathrm{NaCl}$$? (Molar mass of $$\mathrm{NaCl} = 58.5 g/$$mol)

Accepted Answer

1 mole

Question 8

Which of the following elements is most likely to gain electrons during a chemical reaction?

Accepted Answer

Chlorine (Cl)

Question 9

What is the main reason water ($$\mathrm{H_2O}) is a $$polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, creating a partial negative charge on the oxygen side.

Question 10

If 2 moles of methane ($$\mathrm{CH_4$}) $$react with excess oxygen, how many moles of water ($$\mathrm{H_2O}) $$are produced according to the balanced equation $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$?

Accepted Answer

4 moles

Question 11

Which of the following best describes the role of coefficients in a balanced chemical equation?

Accepted Answer

They show the ratio of reactants and products needed to conserve mass.

Question 12

Which group of elements in the periodic table is most likely to form positive ions by losing electrons?

Accepted Answer

Group IA (alkali metals)

Question 13

A student mixes 2.0 moles of sodium ($$\mathrm{Na}) $$with 1.0 mole of lead(II) nitrate ($$\mathrm{Pb(NO_3$)_2}). $$According to the balanced equation $$\mathrm{2Na + Pb(NO_3$)_2 \rightarrow 2NaNO_3 + Pb}$$, what is the limiting reactant?

Accepted Answer

Lead(II) nitrate ($$\mathrm{Pb(NO_3$)_2})$$

Question 14

Which of the following statements about balancing chemical equations is correct?

Accepted Answer

The total mass of reactants must equal the total mass of products.

Question 15

Which of the following best explains why magnesium (Mg) forms a $$2+$$ ion?

Accepted Answer

Magnesium has two valence electrons, which it loses to achieve a stable electron configuration.

Question 16

Which of the following is NOT a correct statement about chemical reactions?

Accepted Answer

Chemical reactions always produce only one product.

Question 17

What is the molar mass of $$\mathrm{Pb(NO_3$)_2}$$? (Pb = 207, N = 14, O = 16)

Accepted Answer

331 g/mol

Question 18

Which of the following best describes the difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, while nonpolar covalent bonds involve equal sharing.

Chemical Reactions: Valence Electrons, Bonding, and Quantities in Reactions

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