# Which has maximum number of molecules?

A. 7gm N_{2}

B. 2gm H_{2}

C. 16gm NO_{2}

D. 16gm O_{2}

[CBSE AIPMT 2002]
In 7gm N_{2},

the number of molecules = 7/28 mol

= 0.25 x N_{A}

In 2gm H_{2},

the number of molecules = 2/2 mol

= 1 x N_{A}

In 16gm NO_{2},

the number of molecules = 16/46 mol

= 0.348 x N_{A}

In 16gm 0_{2},

the number of molecules = 16/32 mol

= 0.5 x N_{A}

Hence, the maximum number of molecules is in 2gm of H_{2}

So, the correct option is B.