Free Jamb Chemistry Past Questions with Solutions

To pass JAMB Chemistry, focus on thoroughly understanding the JAMB syllabus for chemistry and on developing a solid understanding of key concepts. It is essential to practice regularly with past JAMB chemistry questions, prioritize time management, join study groups, attend tutorials, and specifically target your weaker areas by studying relevant topics and practicing related problems diligently. Remember to memorize important formulas and chemical reactions.

Practice online with our comprehensive JAMB Physics Past Questions with solutions here:

JAMB: CHEMISTRY

Here are free JAMB Chemistry past questions for your practice;

Question 1:

If an element has the electronic configuration 1s²2s²2p⁶3s²3p⁴, it is

A. a metal
B. an alkaline earth metal
C. an s-block element
D. a p-block element

Explanation:

1s²2s²2p⁶3s²3p⁴; The element belongs to group 6, which falls in p-block.

The last shell of this element has the configuration “3s²3p⁴“, which means it has 6 valence electrons, placing it in Group 6.

By counting the total electrons (16), we can identify the element as Sulfur.

Question 2:

What is the formula of sodium gallate if gallium (Ga) shows an oxidation number of + 3?

A. NaGaO₃
B. NaGa(OH)₃
C. NaGa(OH)₃
D. NaGa(OH)₄

Explanation:

NaGa(OH)₄

The oxidation number of Na is 1, oxygen is -2, and hydrogen is 1. To find the oxidation number of Ga;

(1) + (Ga) + ([-2 × 4] + [4 × 1]) = 0

1 + Ga + (-8 + 4) = 0

1 + Ga – 4 = 0

Ga = +3

Question 3:

The three-dimensional shape of methane is

A. hexagonal
B. trigonal
C. linear
D. tetrahedral

Explanation:

Answer: tetrahedral

Question 4:

The gaseous product of the reaction between dilute trioxonitrate(V) acid and copper turnings is

A. NO
B. NO₂
C. N₂O₂
D. N₂O₄

Explanation:

For dilute HNO₃

\(\scriptsize 3Cu \: + \: 8HNO_3 \: \rightarrow \: 3Cu(NO_3)_{2(aq)} \: + \: 4H_2O_{(l)} \: + \: 2NO_{(g)} \)

In this equation, copper (Cu) reacts with trioxonitrate(V) (HNO₃) to produce copper(II) nitrate (Cu(NNO₃)₂), nitrogen monoxide (NO), and water (H₂O).

During the reaction, the copper atoms are oxidized by the nitrate ions in nitric acid to form copper(II) ions (Cu²⁺), while the nitrate ions are reduced to nitrogen monoxide (NO). The water molecules are produced as a byproduct of the reaction.

Overall, the reaction between copper and trioxonitrate(V) is a redox reaction, where oxidation and reduction occur simultaneously. This reaction is commonly used in the laboratory for the preparation of copper(II) nitrate.

Question 5:

On the basis of the electrochemical series, which of these ions will show the greater tendency to be discharged at the cathode in an electrolytic cell

A. \( \scriptsize Cu^{2+} \)
B. \( \scriptsize Sn^{2+} \)
C. \( \scriptsize Fe^{2+} \)
D. \( \scriptsize Zn^{2+} \)

Explanation:

Explanation

Electrochemical series, also known as activity series, describes the arrangement of elements in order of their increasing electrode potential.

K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Ag > Au.

1. The elements in the lower position get discharged more easily during electrolysis.
2. The cations can easily gain electrons for the elements.
3. Cu²⁺ discharged more preferentially at the cathode.
4. Zn²⁺ discharged least preferentially at the cathode.

Order of preferential discharge at the cathode:

Cu²⁺ > Sn²⁺ > Fe²⁺ > Zn²⁺