Q: How many grams of CO₂ are produced when 35 grams of methane ($$CH_4) $$are combusted in excess oxygen? ($$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$; molar mass CH_4$ = 16 g/$$mol, $$CO_2 = 44$ g/mol)

$$35 \text{ g } CH_4$ \times \frac{1 \text{ mol } CH_4$}{16 \text{ g}} \times \frac{1 \text{ mol } CO_2$}{1 \text{ mol } CH_4$} \times \frac{44 \text{ g } CO_2$}{1 \text{ mol } CO_2$} = 96.25 \text{ g } CO_2$

Q: 100 grams of steam at 120°C is cooled to 25°C. How much energy is removed from the water? ($$C_{water(gas)} = 1.9 \text{ J/g}^\circ C$$, $$C_{water(liquid)} = 4.18 \text{ J/g}^\circ C$$, $$\Delta H_{fus} = 334 \text{ J/g}$$, $$\Delta H_{vap} = 2260 \text{ J/g})$$

$$Q = 100 \times 1.9 \times (120-100) + 100 \times 2260 + 100 \times 4.18 \times (100-25) = 3800 + 226000 + 31350 = 261150 \text{ J}$$

Question 1

Which of the following best explains why metallic substances tend to be malleable, while ionic and covalent substances are often brittle?

Accepted Answer

Metallic bonds allow atoms to slide past each other without breaking the bond, while ionic and covalent bonds break when layers shift.

Question 2

Given the following compounds: HF, NaCl, SiH₄, and CO₂, which has the highest boiling point and why?

Accepted Answer

HF, because it forms strong hydrogen bonds between molecules.

Question 3

Which of the following metals has the highest melting point: Li, Na, K, or Be? Explain your reasoning.

Accepted Answer

Be, because it has a higher charge density and stronger metallic bonding.

Question 4

Order the following compounds from lowest to highest lattice energy: KI, CaCO₃, CaO. What is the main factor influencing this trend?

Accepted Answer

KI \u003c CaCO₃ \u003c CaO; lattice energy increases with higher charge and smaller ionic radius.

Question 5

Which of the following compounds is most likely to be insoluble in water and why?

Accepted Answer

CaO, because it forms a strong ionic lattice that does not dissociate easily in water.

Question 6

Which of the following molecules is hydrophobic?

Accepted Answer

CF₄, because it is nonpolar and does not interact well with water.

Question 7

Do covalent compounds generally dissociate in water? What is the main exception?

Accepted Answer

No, except for acids, which can dissociate to produce ions.

Question 8

A balloon is released and rises to a region where the atmospheric pressure is 0.5 atm. What happens to the volume of the balloon, assuming temperature is constant?

Accepted Answer

The volume increases because the external pressure decreases.

Question 9

How many grams of CO₂ are produced when 35 grams of methane ($$CH_4) $$are combusted in excess oxygen? ($$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$; molar mass CH_4$ = 16 g/$$mol, $$CO_2 = 44$ g/mol)

Accepted Answer

$$35 	ext{ g } CH_4$ 	imes \frac{1 	ext{ mol } CH_4$}{16 	ext{ g}} 	imes \frac{1 	ext{ mol } CO_2$}{1 	ext{ mol } CH_4$} 	imes \frac{44 	ext{ g } CO_2$}{1 	ext{ mol } CO_2$} = 96.25 	ext{ g } CO_2$

Question 10

100 grams of steam at 120°C is cooled to 25°C. How much energy is removed from the water? ($$C_{water(gas)} = 1.9 	ext{ J/g}^\circ C$$, $$C_{water(liquid)} = 4.18 	ext{ J/g}^\circ C$$, $$\Delta H_{fus} = 334 	ext{ J/g}$$, $$\Delta H_{vap} = 2260 	ext{ J/g})$$

Accepted Answer

$$Q = 100 	imes 1.9 	imes (120-100) + 100 	imes 2260 + 100 	imes 4.18 	imes (100-25) = 3800 + 226000 + 31350 = 261150 	ext{ J}$$

Question 11

Given the reaction $$2H_2(g) + O_2$(g) ightarrow 2H_2O(l)$$ with $$\Delta H_{rxn} = -600 	ext{ kJ/mol}$$, how much energy is released when 0.5 moles of $$H_2$$ react with 0.25 moles of $$O_2$$?

Accepted Answer

$$0.5 	ext{ mol } H_2$ 	imes \frac{1 	ext{ mol rxn}}{2 	ext{ mol } H_2$} 	imes 600 	ext{ kJ} = 150 	ext{ kJ}$$

Question 12

What does a Bronsted acid do?

Accepted Answer

Donates a $$H^+$$ ion.

Question 13

Which of the following will increase the amount of HF produced in the equilibrium: $$HF(aq) + H_2O \rightleftharpoons H_3O^+(aq) + F^-(aq)$$?

Accepted Answer

Adding NaClO$$_4$$, which does not affect the equilibrium.

Question 14

Why does adding water to an equilibrium mixture shift the equilibrium toward the side with more particles?

Accepted Answer

Dilution decreases concentration, so the system shifts to increase the number of particles to counteract the change.

Question 15

If you add HCl (a strong acid) to a solution, what will happen to the pH?

Accepted Answer

The pH will decrease because $$[H^+]$$ increases.

Question 16

Which of the following best describes what pressure is in terms of particle behavior?

Accepted Answer

Force exerted by gas particles on surfaces.

Intro to Chemistry Study Guide: Bonding, Properties, Reactions, and Acids/Bases

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