Question

150 ml of ethyl alcohol is diluted by adding water, then the molarity of a solution is:

(Given, the density of ethyl alcohol $=0.78$)

• A. $2.54$
• B. $11.7$
• C. $2.99$
• D. $3.99$

Answer 1

The correct option is C $2.99$

mass of $C_2{H}_{5}OH=$ density$\times$volume

$=0.78\times 150$

$=117gm$

$\therefore$ moles of $C_2{H}_{5}OH=\frac{117}{46}=2.54$ moles

mass of water$=$Volume of water$=850g=0.85kg$

$\therefore$ Molarity$=\frac{molesof{C}_2{H}_{5}OH}{massofwater}=\frac{2.54}{0.85}=2.99$