Advertisements
Advertisements
Question
What amount of heat must be supplied to 2.0 x 10-2 kg of nitrogen (at room temperature) to raise its temperature by 45 °C at constant pressure? (Molecular mass of N2 = 28; R = 8.3 J mol-1 K-1.)
Advertisements
Solution 1
Mass of nitrogen, m = 2.0 × 10–2 kg = 20 g
Rise in temperature, ΔT = 45°C
Molecular mass of N2, M = 28
Universal gas constant, R = 8.3 J mol–1 K–1
Number of moles, `n = m/M`
`= (2.0xx10^(-2)xx10^3)/28 = 0.714`
Molar specific heat at constant pressure for nitrogen, `C_P = 7/2 R`
`= 7/2 xx 8.3`
`= 29.05 J mol^(-1) K^(-1)`
The total amount of heat to be supplied is given by the relation:
ΔQ = nCP ΔT
= 0.714 × 29.05 × 45
= 933.38 J
Therefore, the amount of heat to be supplied is 933.38 J.
Solution 2
Here, mass of gas,` m= 2xx 10^-2 kg` = 20 g
rise in temperature, `triangleT = 45 ^@C`
Heat required, triangleQ = ?, Molecular mass, M = 28
Number of moles , `n = m/M = 20/28 = 0.714`
As nitrogen is a diatomatic gas,molar specific heat at constant pressure is
`C_p = 7/2R = 7/2 xx 8.3 J mol^(-1) K^(-1)`
As `triangleQ = nC_p triangleT`
`:. triangleQ = 0.714 xx 7/2 xx 8.3 xx 45 J = 933.4 J`
RELATED QUESTIONS
A child running a temperature of 101°F is given an antipyrin (i.e. a medicine that lowers fever) which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought down to 98 °F in 20 min, what is the average rate of extra evaporation caused, by the drug? Assume the evaporation mechanism to be the only way by which heat is lost. The mass of the child is 30 kg. The specific heat of human body is approximately the same as that of water, and latent heat of evaporation of water at that temperature is about 580 cal g–1.
Define heat capacity and state its SI unit.
A solid of mass 50 g at 150 °C is placed in 100 g of water at 11 °C when the final temperature recorded is 20 °C. Find the specific heat capacity of the solid. (specific heat capacity of water = 4.2 J/g °C)
You have a choice of three metals A, B, and C, of specific heat capacities 900 Jkg-1 °C-1, 380 Jkg-1 °C-1 and 460 Jkg-1 °C-1 respectively, to make a calorimeter. Which material will you select? Justify your answer.
Calculate the mass of ice required to lower the temperature of 300 g of water 40°C to water at 0°C.
(Specific latent heat of ice = 336 J/g, the Specific heat capacity of water = 4.2J/g°C)
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].
Why do the farmers fill their fields with water on a cold winter night?
Explain the term boiling ?
State the effect of enhancement of green house effect.
How will rise in sea level affect population in coastal countries?
How will global warming disturb the ecological balance?
The ratio of specific heat capacity to molar heat capacity of a body _____________ .
A burner raises the temperature of 360 g of water from 40°C to 100°C in 5 minutes. Calculate the rate of heat supplied by the burner.
A liquid X has specific heat capacity higher than the liquid Y. Which liquid is useful as coolant in car radiators.
A piece of iron of mass 2.0 kg has a heat capacity of 966 J K-1. Find its specific heat capacity in S.I unit.
Water boils at 120 °C in a pressure cooker. Explain the reason.
m kg of a substance of specific heat capacity s J/kg °C is heated so that its temperature rises from θ1°C to θ2°C. Write down the expression for the heat Q supplied.
Name the substance which has maximum specific heat capacity.
Write the approximate values of the specific latent heat of fusion of ice.
Why is specific heat capacity taken as a measure of thermal inertia?
A certain amount of heat Q will warm 1 g of material X by 3°C and 1 g of material Y by 4°C. Which material has a higher specific heat capacity?
If, in a central heating system, steam enters a radiation pipe at 100°C and water leaves the radiation pipe at 100°C, can this radiation pipe heat a room? Give an explanation for your answer.
Why are athletes advised to put on extra clothes after competing on event?
Will the value of specific heat’capacity and specific latent heat of a substance change if the scale is °F instead of °C?
A vessel of negligible heat*capacity contains 40g of ice in it at 0°C, 8g of steam at 100°C is passed into the ice to melt it. Find the final temperature of the contents of the vessel.
(Specific latent heat of vaporization of steam = 2268 J/g, specific latent heat of fusion of ice = 336 J/f and specific heat capacity of water = 4.2 J/g°C)
Calculate the ratio of two specific heats of polyatomic gas molecules.
How much heat energy is necessary to raise the temperature of 5 kg of water from 20°C to 100°C?
Write the name.
The amount of heat absorbed at constant temperature by unit mass of a liquid to convert into gaseous phase.
Write a short note.
Specific heat capacity
Express the change in internal energy in terms of molar specific heat capacity.
Which of the following substances (A, B and C) has the highest specific beat?
Which of the substances P, Q, or R has the lowest specific heat? The temperature v/s time graph is shown ______.
If 'f' is the number of degrees of freedom of a molecule of a gas and ratio of molar specific heats of a gas, ϒ = 1 + `2/"f"` where ϒ = Cp/Cv. The ratio of 'ϒ' for monoatomic gas to 'ϒ' for (rigid) f diatomic gas is ______.
The diagram below shows a cooling curve for 200 g of water. The heat is extracted at the rate of 100 Js-1. Answer the questions that follow:
- Calculate specific heat capacity of water.
- Heat released in the region BC.
Two cylinders of equal height and radius are made of copper and aluminum. Which of them conducts heat faster?
What is the amount of heat required to raise the temperature of 5 kg of iron from 30°C to 130°C? Specific heat capacity of iron = 483 Jkg-1C-1.
Find the odd one out:
When two kilocalories of heat are supplied to a system, the internal energy of the system increases by 5030 J and the work done by the gas against the external pressure is 3350 J. Calculate J, the mechanical equivalent of heat.
