4. A gas is collected at 20.0 °C and 755.0 mmHg. When the
temperature is changed to -5 °C, what is the resulting pressure?


Answer :

Answer:

[tex]690.61\text{ mmHg}[/tex]

Explanation:

Here, we want to get the resulting pressure

According to the pressure law, temperature and pressure are directly proportional

Mathematically:

[tex]\frac{P_1}{T_1}\text{ = }\frac{P_2}{T_2}[/tex]

where:

P1 is the initial pressure which is 755 mmHg

P2 is the final pressure which is not given

T1 is the initial temperature which we will convert to Kelvin by adding 273.15 K : 20 + 273.15 = 293.15 K

T2 is the final temperature which is -5 + 273.15 = 268.15 K

Substituting the values, we have it that:

[tex]\begin{gathered} \frac{755}{293.15}\text{ = }\frac{P_2}{268.15} \\ \\ P_2\text{ = }\frac{755\times268.15}{293.15}\text{ = 690.61 mmHg} \end{gathered}[/tex]