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Specific Heat Capacity

Chemical reac...

Question

Chemical reactions are invariably associated with the transfer of energy either in the form of heat or light. In the laboratory,
heat changes in physical and chemical processes are measured with an instrument called Calorimeter. Heat change
in the process is calculated as
$q = m s Δ T$ ........ $s = s p e c i f i c h e a t$
$= c Δ T$ ....... $c = h e a t c a p a c i t y$
Heat of reaction at constant volume is measured using bomb Calorimeter.
$q_{V} = Δ U = i n t e r n a l e n e r g y c h a n g e$
Heat of reaction at constant pressure is measured using bomb Calorimeter.
$q_{P} = Δ H$
$q_{P} = q_{V} + P Δ V$
$Δ H = Δ U + Δ n R T$ The enthalpy of fusion of ice is $6.02 k J m o l^{- 1}$ . The heat capacity of water is $4.18 J g^{- 1} C^{- 1}$ .

What is the smallest number of ice cubes at $0^{\circ} C$ , each containing one mole of water, that is needed to cool $500 g$ of liquid water from $20^{\circ} C$ to $0^{\circ} C$ .

A

8

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B

7

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C

140

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D

120

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Solution

The correct option is B 7
heat released to cool $500 g$ water from $20^{\circ} C$ to $0^{\circ} C$ .

$q = m s Δ T$

$= 500 \times 4.18 \times 20 = 41800 J$

$= 41.8 k J$

Number of moles of water(ice) that will melt to absorb $41.8 k J = \frac{q}{E n t h a l p y o f f u s i o n} = \frac{41.8}{6.02}$

$= 6.94 \approx 7$ .

Hence, the correct option is $B$

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Similar questions

Chemical reaction is invariably associated with the transfer of energy either in the form of heat or light. In the laboratory, heat changes in physical and chemical processes are measured with an instrument called Calorimeter. Heat change in the process is calculated as :

q = m s Δ T

s = s p e c i f i c h e a t

= c Δ T

c = h e a t c a p a c i t y

Heat of reaction at constant volume is measured using bomb Calorimeter.

q_{V} = Δ U =

internal energy change
Heat of reaction at constant pressure is measured using bomb Calorimeter.

q_{P} = Δ H

q_{P} = q_{V} + P Δ V

Δ H = Δ U + Δ n R T

The heat capacity of a bomb calorimeter is

500 J K^{- 1}

0.1 g

of Methane was burnt in this calorimeter, the temperature rose by

2^{\circ} C

Δ U

per mole will be :

Q. The enthalpy of fusion of ice is

6.02 k J m o l^{- 1}

. The heat capacity of water is

4.18 J g^{- 1} C^{- 1}

. What is the smallest number of ice cubes at

0^{\circ} C

, each containing one mole of water, that are needed to cool

500 g

of liquid water from

20^{\circ} C

0^{\circ} C

.

the enthaipy of fusion of ice is 6.02 kj/mole the heat capacity of water is 4.18 joule g^-1C^-1 what is the smallest number of ice cubes at 0⁰C each containing one mole of water that are needed to cool 500 g of liquid water from 20^oC - 30^oC

ans =7 how ?

Q. Calculate the mass of ice needed to cool

150

g of water contained in a calorimeter of mass

50

32^{o}

C such that the final temperature is

5^{o}

C.
Specific heat capacity of calorimeter

= 0.4 J / g^{o} C

Specific heat capacity of water

= 4.2 J / g^{o} C

Latent heat capacity of ice

= 330 J / g

.

Q. A bomb calorimeter is used to measure the value of heat of reaction at a constant

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