A student decreases the temperature of a 556 cm3 balloon from 278k to 231k, assuming constant pressure, what should the new volume of the balloon be?

To solve this we assume that the gas inside the balloon is an ideal gas. Then, we can use the ideal gas equation which is expressed as PV = nRT. At a constant pressure and number of moles of the gas the ratio T/V is equal to some constant. At another set of condition of temperature, the constant is still the same. Calculations are as follows:

T1 / V1 = T2 / V2

V2 = T2 x V1 / T1

V2 = 231 x 556 / 278

V2 = 462 cm³