In this question, we have a situation where a gas is in constant pressure but changing its volume and temperature, and the best way to solve a situation like this, is through the Charles's gas law formula, which shows the relationship between volume and temperature when the pressure is constant. The formula is:
V1/T1 = V2/T2
We have:
V1 = 0.510 L
T1 = 19°C, but we need it in Kelvin, 292 K
V2 = ?
T2 = 6°C, or 279 K
Now we add these values into the formula:
0.510/292 = V2/279
0.00175 = V2/279
V2 = 0.488 Liters is the new volume