Question

Determine the empirical formula of Kelvar, used in making bullet proof vests, is 70.6% $C$, 4.2% $H$, 11.8% $N$ and 13.4% $O$:

• A. $C_7{H}_{5}N{O}_2$
• B. $C_7{H}_5{N}_{2}O$
• C. $C_7{H}_{9}NO$
• D. $C_7{H}_{5}NO$

Answer 1

The correct option is D $C_7{H}_{5}NO$

Let the mass of compound be 100g

$C=70.6g=$$\frac{70.6}{12}$ moles =5.88 moles

$H=4.2g=$$\frac{4.2}{1}$ moles =4.2 moles

$N=11.8g=$$\frac{11.8}{14}$ moles =0.84 moles

$O=13.4g=$$\frac{13.4}{16}$ moles =0.84 moles

$C:H:N:O=5.88:4.2:0.84:0.84$

$C:H:N:O=7:5:1:1$

Therefore, empirical formula of Kelvar is $C_7{H}_{5}NO$