Charles's law | 1st year chemistry chapter 3 important short questions notes
Define Charles’s law. Give its
mathematical equation.
Ans. Charles’s law : The volume of the given mass of a gas is directly
proportional to the absolute temperature at constant pressure.
Mathematically: 
V/T =K OR V1/T1 = V2T2 at constant P and number of moles.
Define Charles’s law in terms of
absolute scale of temperature.
Ans. At constant pressure, the volume of the given mass of a gas
increases or decreases by 1/273 of its original volume at 0oC for
every 1oC rise or fall in temperature respectively.
Charles’s law is not obeyed when the
temperature is measured on Celsius scale. Justify it
Ans. Applying Charles’s law on given
data in table
It is observed that, two sides of equation
are not equal. So it is concluded that, Charles’s law is not being obeyed when
temperature is measured on the Celsius scale.
Give the concept of absolute zero.
Ans. The hypothetical temperature at which the
volume of a gas is supposed to become zero
if the gas remains in gaseous state.
0K
= - 273.16oC = -459oF
What is absolute scale of
temperature?
Ans. It is that temperature scale which starts from
– 273.16oC as zero. This is also called Kelvin scale of temperature.
What is absolute zero? What happens
to real gases while approaching it?
Ans. The hypothetical temperature at which the
volume of a gas is supposed to become zero
if the gas remains in gaseous state.
0K
= - 273.16oC = -459oF
All real gases are converted to liquids
above this temperature.
A gas occupies 100 dm3 at
283 K. what will be its volume at -2730C
at constant pressure?
Ans. All the gases are converted into the liquid
state before reaching -2730C. It means that the concerned gas is
liquid at -273oC . So, volume of this gas at -273oC
cannot be predicted.
Throw some light on the factor 1/273
in Charles’s law.
Ans. At constant pressure, the volume of the given mass of a gas
increases or decreases by 1/273 of its original volume at 0oC for
every 1oC rise or fall in temperature respectively.
Justify that the volume of given
mass of a gas becomes theoretically zero at – 273oC.
According to equation:
This equation shows that the volume of given mass of a gas becomes theoretically zero at –
273oC.
How do you explain that -273oC
is theoretical temperature and is not attainable?
Ans. The volume of
given mass of a gas becomes theoretically zero at – 273oC.
Actually gases become liquids before reaching -273oC.
Hence -273oC is not attainable temperature. If volume of gas would
have been zero in laboratory, then law of conservation of mass would have been
violated.
What are various scales of thermometry?
Convert 80oC to Fahrenheit.
Ans. There are three scales of thermometry.
i)
Centigrade
(oC)
ii)
Fahrenheit
(oF)
iii)
Kelvin scale (K)
The temperature
on Fahrenheit is 176o.
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