Chemistry Questions and Answers

Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.

HOT! Click here to get our updates directly on your WhatsApp

1,516.

If 20 cm3 of distilled water is added to 80cm 3 of 0. 50 mol dm-3 hydrochloric acid, the new concentration of the acid will be

0.10mol dm^-3

0.20mol dm^-3

0.40mol dm^-3

2.00mol dm^-3

View answer & explanation

Correct answer is C

\(V_1\) = 80cm3, \(C_1\) = 0.5mol/dm3

\(C_2\) = ? \(V_2) = 20cm3 + 80cm3 = 100cm3

using the dilution formula, \(C_1 V_1 = C_2 V_2\)

0.5 x 80 = \(C_2\) x 100

\(C_2 = \frac{ 40}{100}\) = 0.4mol\(dm^{-3}\)

1,517.

If 1 mole of sodium contains 6 x 10²³ atoms, how many atoms are contained in 0.6 g of sodium? [Na = 23]

1.56 x 10²³

1.56 x 10²²

3.6 x 10²³

3.6 x 10²²

View answer & explanation

Correct answer is B

23g of sodium contain 6 x 10₂₃ atoms :. 0.6g of sodium will contain \(\frac{0.6 x 6 x 10²³}{23}/) = 1.56 x 10²²

1,518.

An atom ²³⁸₉₂X decays by alpha particle emission to give an atom Y. The atomic number and mass number of Y are

90 and 234 respectively

91 and 238 respectively

92 and 236 respectively

93 and 238 respectively

View answer & explanation

Correct answer is A

238₉₂ X 234 ₉₀Y + ^{4 ₂ He Atomic number is 90 while mass number is 234}

1,519.

An element X has isotopic masses of 6 and 7. if the relative abundance is 1 to 12.5 respectively, what is the relative atomic mass of X?

6.0

6.1

6.9

7.0

View answer & explanation

Correct answer is C

Contribution by isotope 6 = 6 x 1 = 6
contribution by isotope 7 = 7 x 12.5 = 87.5
This contribution is made by 1 + 12.5 = 13.5 atoms
Relative atomic mass of = 87.5 + 6 = 93.5/13.5 = 6.9

1,520.

How many orbitals are in the d-sub shell?