Answer
(a)
$$ 728 \space mmHg$$
(b)
$$ 817 \space mmHg$$
Work Step by Step
(a)
1. Since the difference of height is negative, we write the expression as:
$$P_{gas} = P_{atm} - P_{Hg}$$
2. Reading the difference of height between the fluids, we get around 2.3 cm, which is equal to 23 mm:
$$P_{Hg} \approx 23 \space mmHg$$
3. Calculate the pressure of the gas:
$$P_{gas} = 751.5 \space mmHg - 23 \space mmHg = 728 \space mmHg$$
(b)
1. Write the expression
$$P_{gas} = P_{Hg} + P_{atm}$$
2. Reading the difference of height between the fluids, we get around 6.6 cm, which is equal to 66 mm:
$$P_{Hg} \approx 66 \space mmHg$$
3. Calculate the pressure of the gas:
$$P_{gas} = 66 \space mmHg + 751.5 \space mmHg = 817 \space mmHg$$
