Advertisements
Advertisements
Question
How much heat energy is released when 5.0 g of water at 20℃ changes into ice at 0℃? Take specific heat capacity of water = 4.2 J g-1 K-1, Specific latent heat of fusion of ice = 336 J g-1.
Advertisements
Solution
Given,
Mass (m) = 5.0 g
Specific heat capacity of water (c) = 4.2 J g-1 K-1
Specific latent heat of fusion of ice (L) = 336 J g-1
(i) Heat energy released when water lowers it's temperature from 20° C to 0° C
= m × c × change in temperature
Substituting the values in the formula we get,
Q1 = 5 × 4.2 × (20 − 0)
Q1 = 5 × 4.2 × 20
⇒ Q1 = 420 J
(ii) Heat energy released when water at 0° C changes into ice at 0° C = m × L
Substituting the values in the formula we get,
Q2 = 5 × 336 J
⇒ Q2 = 1680 J
From relation,
Q = Q1 + Q2
Q = 420 + 1680
Q = 2100
Total heat released = 2100 J
APPEARS IN
RELATED QUESTIONS
Water in lakes and ponds do not freeze at once in cold countries. Give a reason is support of your answer.
Heat energy is supplied at a constant rate to 100g of ice at 0 °C. The ice is converted into water at 0° C in 2 minutes. How much time will be required to raise the temperature of water from 0 °C to 20 °C? [Given: sp. heat capacity of water = 4.2 J g-1 °C-1, sp. latent heat of ice = 336 J g-1].
Name a liquid which has the highest specific heat capacity.
Why do the farmers fill their fields with water on a cold winter night?
Without green house effect, the average temperature of earth’s surface would have been:
(a) – 18℃
(b) 33℃
(c) 0℃
(d) 15℃
Indian style of cooling drinking water is to keep it in a pitcher having porous walls. Water comes to the outer surface very slowly and evaporates. Most of energy needed for evaporation is taken from the water itself and the water is cooled down. Assume that a pitcher contains 10 kg of water and 0.2 g of water comes out per second. Assuming no backward heat transfer from the atmosphere to the water, calculate the time in which the temperature decrease by 5°C. Specific heat capacity of water = 4200 J kg−1 °C−1 and latent heat of vaporization of water = 2.27 × 106 J kg−1.
Give two reasons as to why copper is preferred over other metals for making calorimeters.
Derive Meyer’s relation for an ideal gas.
Two metals A and B have specific heat capacities in the ratio 2:3. If they are supplied same amount of heat then
Which metal piece will have greater mass if the rise in temperature is the same for both metals?
