Question

A balloon with a volume of 1.50 L is put in liquid nitrogen (temperature is –195.8 ºC, 77.2 K), shrinking its volume to 0.40 L. In kelvins, what was the balloon’s original temperature?
a)46.0 K
b)85.0 K
c)220 K
d)290 K

Answer 1

According to Charles law, we know, at constant pressure, volume is directly proportional to temperature. 
So, V/T = constant 

V₁/t₁ = V₂/t₂
V₁t₂ = V₂t₁

Here, we have: V₁ = 1.50 L
V₂ = 0.40 L
T₂ = 77.2 K
T₁ = ?

Substitute their values into the expression:
1.50 × 77.2 = 0.40 × T₁ 
T₁ = 115.8 / 0.40
T₁ = 289.5
After rounding-off to unit place value, it would be equal to 290 K

So, In short Option D would be your correct answer.

Hope this helps!