1)​
​
We have an empty soda can with a volume of ​
355 mL​
. It is placed on a hot plate and the gas inside is heated to ​
100 °C​
. Then, the can is quickly placed into a beaker with water and the gas temperature rapidly decreases to ​
25 °C​
. The pressure is held constant the entire time. What is the final volume of the can? We are given temperature and volume. Also, it is stated that pressure is held constant. Hence, we want the gas law which relates temperature and volume ONLY. Charles’s law. V1
V2
T = T 1
2
Carefully read and assign variables: V 1 = 355 mL T 1 = 100 °C = 373 K T 2 = 25 °C = 298 K Plug and chug: 355 mL 373 K
V
2
= 298 K
Multiply both sides by 298 K (355 mL)(298 K)
373 K
= V 2 283 mL = V 2 2)​
​
A balloon is filled with air to ​
0.478 L​
. It is then placed in a vacuum and the pressure inside the vacuum is reduced to ​
0.123 atm​
. Assuming temperature is constant and that atmospheric pressure is ​
1.03 atm​
, what is the final volume? We are given volume and pressure, and told that temperature is constant. Hence, we want the gas law which relates pressure and volume ONLY. Boyle’s law. P 1V 1 = P 2V 2 Carefully read and assign variables: V 1 = 0.478 L P 1 = 1.03 atm (The balloon was made at atmospheric pressure, before it was vacuumed) P 2 = 0.123 atm Plug and chug: (0.478 L)(1.03 atm) = V 2(0.123 atm) Divide both sides by 0.123 atm (0.478 L)(1.03 atm)
= V 2 (0.123 atm)
4.00 L = V 2 3)​
​
In summertime in Florida, a tire starts the day with a pressure of ​
1.91 atm​
. While driving at 3 p.m., the tire air temperature sensor reads ​
68 °C ​
and the pressure sensor reads ​
2.18 atm​
. What was the approximate temperature of the ambient air in °C? We are looking for the gas law which relates temperature and pressure. Since volume is not mentioned about the tire, assume it is constant. Hence, Gay­Lussac’s law. P1
P2
T = T 1
2
Carefully assign variables P 1 = 1.91 atm P 2 = 2.18 atm T 2 = 68 °C = 341 K Plug and chug: 1.91 atm T1
= 2.18 atm
341 K Cross multiply (341 K)(1.91 atm) = (2.18 atm)T 1 Divide both sides by 2.18 atm (341 K)(1.91 atm)
(2.18 atm)
= T 1 298 K = T 1 = 25 °C