Q) Percentage purity of gold in 10g of chain marked 20carat (puregold=24carat)-
1)80%  2)91.6% 3)83.33% 4)96%
Q) The crystalline salt Na2SO4.xH2O on heating loses 55.9% of its weight ; the value of x in the crystalline salt is -
1)5 2)7 3)2 4)10

Asked by shubhamjindal | 19th Jun, 2014, 11:16: PM

Expert Answer:

Dear shubham.jalandhar@gmail.com

Thanks for asking us a question in Ask the Expert section of TopperLearning.com.

We cannot entertain more than 5 questions in a subject per day. In case of multiple questions within a query, please post each question individually and let us know where you are getting stuck so that we would be able to explain things better.

Regards

Topperlearning Team.
Solution to second question:
The crystalline salt Na2SO4.xH2O on heating loses 55.9% of its weight ; the value of x in the crystalline salt is -
1)5 2)7 3)2 4)10
Correct option: 4

Consider 100g of Na2SO4.x H2O

On heating it loses 55.90g of water.

Mole proportion Na2SO4 = 44.10, H2O = 55.9

Na2SO4 = 44.10 = 0.3106

142

H2O = 55.90 = 3.106

18

So let us divide by the smallest, so we have mole proportion as Na2SO4.H2O = 1:10

So the salt is Na2SO4.10H2O

Answered by Vaibhav Chavan | 20th Jun, 2014, 10:32: AM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.