MCQ
The density of a liquid is $1.5\, g/mL$. There are $50\, drops$ in $5\, mL$. The number of molecules in $1\, drop$ is (molecular weight of liquid is $100$)
- A$1.5 \times 10^{-3}$
- B$1.5 \times 10^{23}$
- ✓$9 \times 10^{20}$
- D$9 \times 10^{26}$
No. of moles in one $\operatorname{drop}=\frac{\mathrm{d} \times \mathrm{V}}{\mathrm{mol} . \mathrm{wt} .}=\frac{5 \times 1.5}{50 \times 100}$
$=1.5 \times 10^{-3}$
Number of molecules in one drop
${=1.5 \times 10^{-3} \times \mathrm{N}_{\mathrm{A}}}$
${=1.5 \times 10^{-3} \times 6 \times 10^{23}}$
${=9.0 \times 10^{20}}$
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$(I)\, CO^{2-}_3$ $(II)\, XeF_4$ $(III)\, I^-_3$ $(IV)\, NCl_3$ $(V)$ $BeCl_2$
[Assume no volume change on adding $\mathrm{NH}_{3}$ ]