JEE Main 2017 · 2 Apr · Shift 1 · Physics Q11

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PhysicsSingle correct+4 / -1Question 11 of 90

The temperature of an open room of volume 30 m $^3$ increases from 17°C to 27°C due to the sunshine. The atmospheric pressure in the room remains $1\times10^5$ Pa. If $n_i$ and $n_f$ are the number of molecules in the room before and after heating, then $n_f-n_i$ will be :

-1.61\times10^{23}

1.38\times10^{23}

2.5\times10^{25}

-2.5\times10^{25}

Answer and worked solution

Official answer: D

$N=\dfrac{PV}{kT}$ at constant P and V:
$n_f-n_i=\frac{PV}k\left(\frac1{300}-\frac1{290}\right)=\frac{10^5\times30}{1.38\times10^{-23}}\times(-1.15\times10^{-4})\approx-2.5\times10^{25}.$

Topics:Ideal gas equation

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JEE Main 2017 · 2 Apr · Shift 1, Physics question 11