2 g of water condenses when passed through 40 g of water initially at 25°C . The- condensation of steam raises the temperature of water to 54.3°C . What is the latent heat of steam?

Question

2 g of water condenses when passed through 40 g of water initially at 25°C . The- condensation of steam raises the temperature of water to 54.3°C . What is the latent heat of steam? (A)  540 cal/g  (B)  536 cal/g  (C)  270 cal/g  (D)  480 cal/g

Tardigrade Admin · Accepted Answer

Heat required to raise the temperature of

40 g

of water from

2 5^{\circ} C

to

54. 3^{\circ} C

, is equivalent to sum of heat required to condense the steam.

∴

Heat required to raise the temperature of water by

t^{\circ} C

is

= m_{1} c Δ t_{1} \dots

(i)
where,

c

is specific heat of water and

m

the mass.
Heat required to condense steam

= m_{2} L + M_{2} c Δ t_{2} \dots

(ii)
Equating Eqs. (i) and (ii), we get

m_{2} L + m_{2} c Δ t_{2} = m_{1} c Δ t_{1}

Given

m_{2} = 2 g

Δ t_{2} = (100 - 54.3)^{\circ} C = 45. 7^{\circ} C

m_{1} = 40 g

Δ t_{1} = (54.3 - 25)^{\circ} C = 19. 3^{\circ} C

= c = 1 c a l g^{- 1}

\Rightarrow 2 \times L + 2 \times 1 \times 45.7

= 40 \times 1 \times 29.3

\Rightarrow 2 L + 91.4 = 1172

\Rightarrow L = 540.3 c a l g^{- 1}

Q. $2 g$ of water condenses when passed through $40 g$ of water initially at $2 5^{\circ} C$ . The- condensation of steam raises the temperature of water to $54. 3^{\circ} C$ . What is the latent heat of steam?

$540 c a l / g$

$536 c a l / g$

$270 c a l / g$

$480 c a l / g$

Q. 2g of water condenses when passed through 40g of water initially at 25∘C . The- condensation of steam raises the temperature of water to 54.3∘C . What is the latent heat of steam?

540cal/g

536cal/g

270cal/g

480cal/g

Q. $2 g$ of water condenses when passed through $40 g$ of water initially at $2 5^{\circ} C$ . The- condensation of steam raises the temperature of water to $54. 3^{\circ} C$ . What is the latent heat of steam?

$540 c a l / g$

$536 c a l / g$

$270 c a l / g$

$480 c a l / g$