Which of the following compounds contain(s) no covalent bond(s)? KCl , PH_3 , O_2 , B_2H_6 , H_2SO_4

Chemical Bonding and Molecular Structure PYQ — JEE Main 2018 · Shift 0 · Q14 with Solution

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Correct answer: D

We need the compound(s) that contain no covalent bond.

Let us examine each substance one by one.
$KCl$
- Potassium is a metal and chlorine is a non-metal.
- $KCl$ is formed by transfer of one electron from $K$ to $Cl$ : $K \to K^+ + e^-$ $Cl + e^- \to Cl^-$
- Hence, $KCl$ is an ionic compound.
- Therefore, it contains no covalent bond.
$PH_3$
- Phosphorus and hydrogen are both non-metals.
- The $P-H$ bonds are formed by sharing of electrons.
- So, $PH_3$ contains covalent bonds.
$O_2$
- In $O_2$ , two oxygen atoms share electrons.
- It has a double covalent bond: $O=O$
- So, $O_2$ contains covalent bonds.
$B_2H_6$
- Diborane is a covalent molecule.
- It contains normal $B-H$ covalent bonds and also three-center two-electron bridges.
- Therefore, it definitely contains covalent bonding.
$H_2SO_4$
- Sulfuric acid is a molecular compound.
- It contains $O-H$ and $S-O$ covalent bonds.
- Therefore, it contains covalent bonds.
Conclusion

Only $KCl$ contains no covalent bond.
Match with options
- A: $KCl$ , $B_2H_6$ $\rightarrow$ incorrect
- B: $KCl$ , $B_2H_6$ , $PH_3$ $\rightarrow$ incorrect
- C: $KCl$ , $H_2SO_4$ $\rightarrow$ incorrect
- D: $KCl$ $\rightarrow$ correct

Therefore, the correct answer is D.