500mL of `NH_(3)` contains `6.02xx10^(23)` molecules at STP. How many molecules are present in 100 mL of `CO_(2)` at STP?

Options

A. `6 xx 10^23`
B. `1.5 xx 10^23`
C. `1.2 xx 10^23`
D. none of these

Answer

C

Explanation

At constant temperature and pressure
`V_1/n_1 =V_2/n_2`
`6.00 xx 10^23` molecules = 1 mole
`500/1 = (100)/(n_2)`
`n_2 = 1//5`
` = 1/5 xx 6.00 xx 10^23 = 1.2 xx 10^23`