Question

Two substances A and B of equal mass m are heated by the uniform rate of $6cal{s}^{-1}$ under similar conditions graph between temperatures and shown in the figure. The ratio of heat absorbed $H_A/H_B$ by them for complete fusion is:

• A. $\frac{9}{4}$
• B. $\frac{4}{9}$
• C. $\frac{8}{5}$
• D. $\frac{5}{8}$

Answer 1

The correct option is C $\frac{8}{5}$

From the curve, the melting point for A is $60{}^{\circ }C$ and the melting point for B is $20{}^{\circ }C$.

The time taken by A for fusion is given as,

$t=6-2$

$t=4minutes$

The time taken by B for fusion is given as,

$t=6.5-4$

$t=2.5minutes$

The ratio of heat observed is given as,

$\frac{H_A}{H_B}=\frac{6\times 4\times 60}{6\times 2.5\times 60}$

$\frac{H_A}{H_B}=\frac{8}{5}$