Question

Water $ + CH_3OH $ mixture shows positive deviation from ideal solution behaviour. $ 100 \,mL $ of water is mixed with $ 100 \,mL $ of $ CH_3OH $ . Then, total volume of the mixture will be

• A. $ 200\, mL $
• B. less than $ 200 \,mL $ because of additional $ H $ -bonding between $ H_2O $ and $ CH_3OH $
• C. more than $ 200\, mL $ because $ H $ -bonding within $ H_2O $ molecules vanishes
• D. more than $ 200\, mL $ because $ H $ -bond between $ H_2O $ and $ CH_3OH $ is weaker than that between $ H_2O $ and $ H_2O $

Answer 1

Answer: (D)

For (+)ve deviation,
$\Delta H >\,0$, attractive forces between the molecules becomes weaker, and $\Delta\,V>\,0$
Thus, on mixing $100 \,mL$ of water with $100\,ml$ of $CH_{3}OH$, the total volume increases, i.e. becomes more than $200\,mL$ $(100+100)$ due to weaker attractive force between $H_{2}O$ and $CH_{3}OH$ molecules