Question

A sample of clay contains $50\%$ silica and $10\%$ water. The sample is partially dried by which it loses $8\text{g}$ water. If the percentage of silica in the partially dried clay is $52$, calculate the percentage of water in the partially dried clay ?

• A. $4.9\%$
• B. $6.4\%$
• C. $0.58\%$
• D. $0.28\%$

Answer 1

The correct option is B $6.4\%$

Let weight of clay be $xg$ initially
so weight of silica $=\frac{50}{100}x=0.5x$
and weight of water $=\frac{10}{100}x=0.1x$
After loss of $8g$ of water
weight of clay will be $(x-8)g$

weight of silica $=\frac{52}{100}(x-8)g$

$=(0.52x-4.16)g$
and weight of silica will be same before and after drying so
$(0.52x-4.16)=0.5x$
this gives $x=208g$

So weight of clay after drying $=208-8=200g$
weight of water initially $=0.1x=0.1\times 208=20.8g$
water loss $=8g$
final weight of water $=20.8-8=12.8g$

so, percentage of water in the final clay sample $=\frac{12.8}{200}\times 100=6.4\%$