Q: Which of the following best explains why the energy of a photon increases as its frequency increases?

Because $$E = h\nu$$, where $$E is $$energy and $$\nu is $$frequency.

Question 1

Which of the following best describes the role of NH₃ in the equilibrium reaction: NH₄⁺(aq) + H₂O(l) ⇌ NH₃(aq) + H₃O⁺(aq)?

Accepted Answer

Brønsted–Lowry base

Question 2

A chemist carries out the reaction of 0.250 mol of Cl₂ with excess F₂ at 250°C and 1.00 atm. What is the maximum volume of ClF₃ that the reaction can produce? (Assume ideal gas behavior.)
Cl₂(g) + 3F₂(g) → 2ClF₃(g)

Accepted Answer

3.41 L

Question 3

Which of the following statements is always correct for a compound?

Accepted Answer

It has a constant composition.

Question 4

A student observes the combustion of propane (C₃H₈). Because of the heat and light it generates, the student concludes that the reaction has NO activation energy. Is the student's conclusion correct, and why?

Accepted Answer

No; because the reaction requires an ignition source, it does have an activation energy.

Question 5

At 25°C, the solubility product constant ($$K_{sp}) $$for MgF₂ is $$3.7 	imes 10$$^{-8}$$. What is the concentration of F⁻ in a saturated solution of MgF₂ at 25°C?

Accepted Answer

$$4.2 	imes 10$$^{-3}$$ M

Question 6

Which of the following chemical reactions involves an increase in the entropy of the system?

Accepted Answer

2HgO(s) → 2Hg(l) + O₂(g)

Question 7

A student mixes 200.0 mL of 0.150 M CaCl₂(aq) with 115.0 mL of 0.250 M Na₃PO₄(aq). What is the maximum number of moles of Ca₃(PO₄)₂ that the reaction can produce?
3CaCl₂(aq) + 2Na₃PO₄(aq) → Ca₃(PO₄)₂(s) + 6NaCl(aq)

Accepted Answer

0.0084 mol

Question 8

Which of the following statements about the boiling point of pure liquid ethanol at 78.5°C is correct?

Accepted Answer

Its vapor pressure is equal to atmospheric pressure.

Question 9

What is the empirical formula of aspartame, given the following composition by mass: C: 57.13%, H: 6.38%, N: 9.52%, O: 25.97%?

Accepted Answer

C₇H₇NO₂

Question 10

Which of the following best explains why the pressure of a gas decreases when the volume of its container is increased at constant temperature?

Accepted Answer

The pressure decreases because there are fewer collisions between gas molecules and the container walls.

Question 11

Which of the following is the correct electron configuration for the chromium ion in Cr₂O₇²⁻?

Accepted Answer

[Ar] 3d³

Question 12

A chemist wants to increase the percent yield of Cl₂ in the equilibrium reaction: COCl₂(g) ⇌ CO(g) + Cl₂(g). Which of the following changes would be most effective?

Accepted Answer

By increasing the volume of the container

Question 13

Which of the following is the correct balanced chemical equation for the reaction of SnO₂ with CO to produce Sn and CO₂, including the states of matter?

Accepted Answer

SnO₂(s) + 2CO(g) → Sn(s) + 2CO₂(g)

Question 14

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It decreases the activation energy of the reaction.

Question 15

A solution is prepared by dissolving 0.50 mol of NaCl in 1.0 kg of water. What is the molality of the solution?

Accepted Answer

0.50 m

Question 16

Which of the following is the correct relationship for calculating the percent yield of a chemical reaction?

Accepted Answer

Percent yield = (actual yield / theoretical yield) × 100

Question 17

Which of the following best explains why the energy of a photon increases as its frequency increases?

Accepted Answer

Because $$E = h
u$$, where $$E is $$energy and $$
u is $$frequency.

Question 18

A 10.0 g sample of aluminum (specific heat capacity $$C = 0.90 	ext{ J/g}^\circ	ext{C}) is $$heated from 25.0°C to 55.0°C. How much heat is absorbed by the sample?

Accepted Answer

270 J

Question 19

Which of the following best describes a mixture?

Accepted Answer

A combination of two or more substances that can be separated by physical means.

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