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Thursday, 11 June 2026
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Chemistry Past Questions and Answers

Jamb 2019 Chemistry Questions

Question 86:
Consider the reaction
A\(_{(s)}\) + 2B\(_{(g)}\) → 2C\(_{(aq)}\) + D\(_{(g)}\)
What will be the effect of a decrease in pressure on the reaction?
  • A The equilibrium will shift
  • B Rate of forward reaction will increase
  • C Rate of backward reaction will increase
  • D Rates of forward and backward reaction are not affected
View Answer & Explanation
Question 87:
For the general equation of the nature
xP + yQ ⇌ mR + nS, the expression for the equilibrium constant is
  • A K[P]\(^x\)[Q]\(^y\)
  • B \(\frac{m[R][S]}{x[P]y[Q]}\)
  • C \(\frac{[P]^x[Q]^y}{[R]^m[S]^n}\)
  • D \(\frac{[R]^m[S]^n}{[P]^x[Q]^y}\)
View Answer & Explanation
Question 88:
Which of the following reactions is an oxidation process?
  • A 2H\(^+\) + 2e\(^-\) \(\to\) H\(_2\)
  • B 2O\(^{2-}\) + 4e\(^-\) \(\to\) O\(_2\)
  • C OCl\(^-\) + H\(_2\)O + 2e\(^-\) \(\to\) 2OH\(^-\) + Cl\(^-\)
  • D Cl + e\(^-\) \(\to\) Cl\(^-\)
View Answer & Explanation
Question 89:
If acidified Potassium Dichromate(VI) (K\(_2\)Cr\(_2\)O\(_7\)) acts as oxidizing agent, color changes from
  • A Yellow to green
  • B Orange to green
  • C Yellow to red
  • D Orange to red
View Answer & Explanation
Question 90:
The heat of formation of ethene, C\(_2\)H\(_4\) is 50 kJmol\(^{-1}\), and that of ethane, C\(_2\)H\(_6\) is -82kJmol\(^{-1}\). Calculate the heat evolved in the process:
C\(_2\)H\(_4\) + H\(_2\) \(\to\) C\(_2\)H\(_6\)
  • A -122kJ
  • B -132kJ
  • C -88kJ
  • D -60kJ
View Answer & Explanation