Question

Which of the following solutions at the same temperature will be isotonic?

• A. 3.42 g of cane sugar in one litre water and 0.18 g of glucose in one litre water
• B. 3.42 of cane sugar in one litre water and 0.18 g of glucose in 0.1 litre water
• C. 3.42 g of cane sugar in one litre water and 0.585 g of NaCl in one litre water
• D. 3.42 g of cane sugar in one litre water and 1.17 g of NaCl in one litre water

Answer 1

The correct option is B 3.42 of cane sugar in one litre water and 0.18 g of glucose in 0.1 litre water

Molecular weight of Glucose $\left(C_6{H}_{12}{O}_6\right)=180$

Molecular weight of Cane sugar $\left(C_{12}{H}_{22}{O}_{11}\right)=342$

Isotonic solutions are the solutions which have same osmotic pressure i.e.., $\pi =iMST$

3.42 g of cane sugar in one litre $=0.01M$

0.18g of glucose in 0. 1 litre which means 1.8g of glucose in 1 litre i.e.., 0.01M.

Here $i=1$ as both do not dissociate.

${\pi }_{glucose}=1\times 0.01\times ST=0.01ST$

${\pi }_{canesugar}=1\times 0.01\times ST=0.01ST$

If molality is same then the solutions are isotonic.