OAT General Chemistry Principles Questions and Answers

Question 1

A spontaneous chemical reaction is observed to have a positive enthalpy change (ΔH > 0) and a positive entropy change (ΔS > 0).
Which of the following statements must be true for this process to be spontaneous?

Accepted Answer

The temperature is high enough for the TΔS term to outweigh the ΔH term.

Answer

The reaction is spontaneous only at low temperatures.

Answer

The reaction is spontaneous at all temperatures.

Answer

The reaction is non-spontaneous at all temperatures.

Question 2

Which of the following correctly describes the effect of adding a catalyst to a chemical reaction that has reached equilibrium?

Accepted Answer

It increases the rate of both the forward and reverse reactions equally.

Answer

It increases the concentration of the products.

Answer

It shifts the equilibrium position to the right.

Answer

It decreases the enthalpy change (ΔH) of the reaction.

Question 3

A researcher has a 0.1 M solution of a weak acid, acetic acid (CH₃COOH), with a Ka of 1.8 x 10⁻⁵. Which of the following species will be present at the lowest concentration in the solution?

Accepted Answer

OH⁻

Answer

CH₃COOH

Answer

H₃O⁺

Answer

CH₃COO⁻

Question 4

According to the Ideal Gas Law, if the volume and the number of moles of a gas are held constant, what is the relationship between its pressure and absolute temperature?

Accepted Answer

They are directly proportional.

Answer

They are inversely proportional.

Answer

They have a logarithmic relationship.

Answer

There is no relationship between them.

Question 5

In the context of quantum mechanics, which quantum number is the primary determinant of the shape of an atomic orbital (e.g., s, p, d, f)?

Accepted Answer

Azimuthal quantum number (l)

Answer

Magnetic quantum number (m_l)

Answer

Principal quantum number (n)

Answer

Spin quantum number (m_s)

Question 6

A scientist is performing an electroplating experiment which involves the following half-reaction: Cu²⁺(aq) + 2e⁻ → Cu(s). Which of the following statements accurately describes this process?

Accepted Answer

Copper is being reduced at the cathode.

Answer

Copper is being oxidized at the anode.

Answer

This is an oxidation half-reaction.

Answer

This reaction occurs at the anode of a galvanic cell.

A spontaneous chemical reaction is observed to have a positive enthalpy change (ΔH > 0) and a positive entropy change (ΔS > 0).Which of the following statements must be true for this process to be spontaneous?

A spontaneous chemical reaction is observed to have a positive enthalpy change (ΔH > 0) and a positive entropy change (ΔS > 0).
Which of the following statements must be true for this process to be spontaneous?