Waec Chemistry 2018 Past Questions and Answers

Question 41:

• WAEC 2018

The law of definite proportions states that

A. Pure samples of the same compound contain the same elements combined in the same proportion by mass
B. Pure samples of substances are in the same proportion by mass
C. Chemical compounds are pure because they contain the same elements
D. Matter can neither be created nor destroyed.

Question 42:

• WAEC 2018

What is the relative molecular mass of a compound which has empirical formula \(CH_{2}O\)? [C= 12, H= 1, O= 16]

A. 42
B. 45
C. 126
D. 180

Question 43:

• WAEC 2018

Atoms are electrically neutral because they

A. Do not conduct electricity
B. Contain equal number of protons and electrons
C. Are composed of neutrons and electrons
D. Cannot be attracted by electromagnetic field.

Question 44:

• WAEC 2018

Common Salt (NaCl) is used to preserve foods. Which of the following properties can be used to determine its purity before use?

A. Solubility in water
B. Melting point
C. Relative density
D. Crystalline nature

Question 45:

• WAEC 2018

Which of the following electron configurations represents the transition element Chromium \(_{24}Cr\)?

A. \(1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{4}\)
B. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{6}\)
C. \(1s^{2}2s^{2}2p^{6}3s^{2}3d^{4} 4s^{1}\)
D. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{5}\)