IB Chemistry 3

Question 1

Which of the following best describes a buffer solution?

Accepted Answer

A solution that resists changes in pH upon addition of small amounts of acid or base

Answer

A buffer resists pH changes because it contains a weak acid and its conjugate base (or weak base and conjugate acid) that neutralize added acid or base.

Question 2

What is the hybridization of the carbon atoms in ethene (C₂H₄)?

Accepted Answer

sp²

Answer

Each carbon in ethene is sp² hybridized, forming three sigma bonds and one pi bond with the double bond.

Question 3

Which type of radioactive decay results in the atomic number increasing by 1?

Accepted Answer

Beta-minus decay

Answer

In beta-minus decay, a neutron converts to a proton, emitting an electron, which increases the atomic number by 1.

Question 4

The rate of a first-order reaction depends on:

Accepted Answer

The concentration of reactant raised to the first power

Answer

For a first-order reaction, the rate = k[A]¹, meaning the rate is directly proportional to the concentration of the reactant.

Question 5

Which colligative property explains why adding salt lowers the freezing point of water?

Accepted Answer

Freezing point depression

Answer

Dissolving a solute in water disrupts the crystalline structure formation, requiring a lower temperature to freeze — this is freezing point depression.

IB - International Baccalaureate Practice Test

IB - International Baccalaureate Practice Test

IB Chemistry 3