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.
How many atoms are contained in 0.2moles of nitrogen? \([N_{A} = 6.02 \times 10^{23}]\)
\(1.20 \times 10^{23}\)
\(2.41 \times 10^{23}\)
\(3.62 \times 10^{23}\)
\(4.82 \times 10^{23}\)
Correct answer is A
\(1 mole = 6.02 \times 10^{23} atoms\)
\(0.2 moles = 6.02 \times 10^{23} \times 0.2\) atoms
= \(1.204 \times 10^{23}\)
\(\approxeq 1.2 \times 10^{23}\)
When chlorine is passed through a sample of water, the pH of the water sample would be
< 7
> 7
= 7
0
Correct answer is A
\(Cl_{2} + H_{2}O \to HCl + HOCl\)
The two compounds in the product end are acidic and hence, their mixture is acidic. Hence, the pH is < 7
One of the criteria for confirming the purity of benzene is to determine its
heat capacity
boiling point
mass
colour
Correct answer is B
Any pure substance will have a specific melting and boiling point. The presence of impurities alters the boiling point of benzene.
Which of the following CANNOT be an empirical formula?
\(CH\)
\(CH_{2}\)
\(P_{2}O_{5}\)
\(N_{2}O_{4}\)
Correct answer is D
The empirical formula is always in the ratio of the smallest positive integer, hence, \(N_{2}O_{4}\) has an empirical formula \(NO_{2}\)
\(Cu\) and \(HNO_{3}\) are not suitable for preparing hydrogen gas because of their
reactivity and oxidation respectively
conductivity and corrosiveness respectively
melting point and reduction respectively
electronegativity and solubility respectively
Correct answer is A
Copper is not active enough to replace hydrogen in an acid. Also, nitric acid is a strong oxidizing agent which quickly oxidises hygrogen to water.