Free CXC Chemistry Question and Answers

Question 1

What are the 3 particles that make-up the atom?

Accepted Answer

protons, neutrons, and electrons

Answer

These three particles - protons, neutrons, and electrons - together form the basic structure of atoms. Protons and neutrons are located in the nucleus, which contains most of the atom's mass and is positively charged due to the presence of protons.
Electrons occupy the space surrounding the nucleus and contribute to the atom's size and chemical behavior. The number of protons in an atom determines its atomic number (Z), which defines the element, while the combined number of protons and neutrons determines the atomic mass number (A).

Question 2

The proper formula for magnesium hydroxide:

Accepted Answer

Mg(OH)2

Answer

"Magnesium hydroxide is a compound composed of magnesium (Mg) and hydroxide (OH) ions. In this compound, magnesium (Mg) has a +2 charge, and the hydroxide (OH) ion has a -1 charge.
The formula Mg(OH)2 indicates that magnesium (Mg) is bonded to two hydroxide (OH) ions. This chemical formula correctly represents the composition and structure of magnesium hydroxide. Each magnesium ion (Mg^2+) is surrounded by two hydroxide ions (OH^-) in the compound. Therefore, the proper formula for magnesium hydroxide is Mg(OH)2."

Question 3

The three types of nuclear radiation in order of increasing penetrating power are

Accepted Answer

alpha, beta, gamma

Answer

The three types of nuclear radiation in order of increasing penetrating power are alpha (α) particles, beta (β) particles, and gamma (γ) rays.

1.Alpha (α) particles: Alpha particles consist of two protons and two neutrons bound together, similar to the nucleus of a helium atom. They have a relatively low penetrating power and can be stopped by a sheet of paper or a few centimeters of air. However, alpha particles can be harmful if ingested or inhaled.
2.Beta (β) particles: Beta particles are high-energy electrons (β^-) or positrons (β^+). They have greater penetrating power compared to alpha particles and can penetrate several millimeters of materials like aluminum. Beta particles can be shielded by thicker materials such as plastic or glass.
3.Gamma (γ) rays: Gamma rays are high-energy electromagnetic waves emitted from the nucleus of an atom during radioactive decay.
They have the highest penetrating power and can pass through several centimeters of dense materials like lead or concrete. Specialized shielding such as lead or concrete is required to protect against gamma rays.
Therefore, the correct order of increasing penetrating power for the three types of nuclear radiation is alpha (α), beta (β), and gamma (γ), represented by option (a) alpha, beta, gamma.

Question 4

How many elements are in C6H12O6?

Accepted Answer

3

Answer

The chemical formula C6H12O6 represents glucose, which is a type of sugar and an organic compound. This formula indicates the composition of glucose in terms of its constituent elements:

1.C6 (carbon): There are 6 carbon atoms in each molecule of glucose.
2.H12 (hydrogen): There are 12 hydrogen atoms in each molecule of glucose.
3.O6 (oxygen): There are 6 oxygen atoms in each molecule of glucose.
Therefore, the compound C6H12O6 consists of 3 elements: carbon (C), hydrogen (H), and oxygen (O). Each element contributes to the molecular structure of glucose, which is essential for energy production in living organisms through cellular respiration.

Question 5

A molecule is made up of

Accepted Answer

One or more atoms.

Answer

A molecule is a group of two or more atoms that are chemically bonded together. These atoms can be of the same element (forming a molecule of an element) or different elements (forming a molecule of a compound). In a molecule, atoms are held together by chemical bonds, such as covalent bonds, where atoms share electrons to achieve stability.

CXC - Caribbean Examinations Council Practice Test

CXC - Caribbean Examinations Council Practice Test

Free CXC Chemistry Question and Answers