Q5.11P - Chemistry: Molecular Nature Of Matter And Change

Question

In Figure P5.11, what is the pressure of the gas in the flask (in kPa) if the barometer reads 765.2 mmHg?

Step-by-Step Solution

Answer

The pressure of the gas is 100.0 kPa.

Step 1: Total pressure

Total pressure is the sum of the pressure of the atmosphere and the difference in heights of the columns.

 

Step 2: Determination of pressure of the gas

Convert cmHg to mmHg

$$\begin{gathered} \text{1} \text{cmHg} \text{ = } \text{10} \text{mmHg} \\ \Rightarrow 1.3 \text{cmHg} \text{ = } 13 \text{mmHg} \end{gathered}$$

The pressure of the gas is,

$\begin{array}{rcl}& & {\text{P}}_{\text{total}}\text{ = ∆h + } {\text{P}}_{\text{gas}}\\ & & {\text{P}}_{\text{gas} }\text{ = } {\text{P}}_{\text{total} }-∆h\\ & & \text{ = 765.2} \text{mmHg} \text{ - } 13 \text{mmHg}\\ & & \text{ = } \text{752.2} \text{mmHg}\\ & & \end{array}$

Now, convert the pressure of the gas from mmHg to kPa,

 1 mmHg = 0.133 kPa

  $\text{752.2} \text{mmHg×}\frac{0.133 \text{kPa}}{1 \text{mmHg}} \text{ = } 100.0 \text{kPa}$

Thus, the pressure of the gas is 100.0 kPa.