Q6 of 100 Page 34

An electric bulb of volume 250 cc was sealed during manufacturing at a pressure of 10–3 mm of mercury at 27°C. Compute the number of air molecules contained in the bulb. Avogadro constant = 6 × 1023 mol–1, density of mercury = 13600 kg m–3 and g = 10 m s–2.

We know ideal gas equation


PV=nRT


Where V= volume of gas


R=gas constant


T=temperature


n=number of moles of gas


P=pressure of gas.


Given


Volume of gas=250cc


1cc=1cm3m3


V=250m3


Pressure P=10–3 mm of mercury


1mm of Hg= 133.32Pa


P= mm of Hg=133.32 Pa


Temperature T=27


T(K)=T ()+273.15


T=T(K)=27+273.15=300.15K


From ideal gas equation, we can write




Number of molecules = Avogadro numbernumber of moles


Number of molecules=n


=


Number of molecules in electric bulb=.


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