Question

a)

Convert 0.500 atm of pressure to its equivalent in millimetres of mercury. Express the pressure numerically in millimetres of mercury.

b)

High-pressure liquid chromatography (HPLC) is a method used in chemistry and biochemistry to purify chemical substances. The pressures used in this procedure range from around 500 kilopascals (500,000 Pa) to about 60,000 kPa (60,000,000 Pa). It is often convenient to know the pressure in torr. If an HPLC procedure is running at a pressure of 3.69×10⁸ Pa , what is its running pressure in torr?

Express the pressure numerically in torr.

c)

A certain gas is present in a 12.0 L cylinder at 1.0 atm pressure. If the pressure is increased to 2.0 atm , the volume of the gas decreases to 6.0 L . Find the two constants ki, the initial value of k, and kf, the final value of k, to verify whether the gas obeys Boyle’s law.

Express your answers to two significant figures separated by a comma.

Answer 1

(a).

Because,

1 atm = 760 mmHg

So,

0.500 atm = 0.500 x 760 mmHg

= 380 mmHg

So,

Pressure in mmHg = 380 mmHg

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(b).

Because,

1 Pa = 0.00750062 torr

So,

3.69×10⁸ Pa = 3.69×10⁸  x 0.00750062 torr

= 2.77 x 10⁶ torr

So,

Pressure in torr = 2.77 x 10⁶ mmHg

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(c).

According to Boyle's law at constant temperature (T),  pressure (P) of the gas is inversely proportional to its volume (V). That is product of pressure and volume remains constant if the temperature becomes constant.

So,

P₁V₁ = K_i ....................(1)

Where, K_i is initial constant of proportionality

Substitute the value of P₁ (Initial pressure) = 1.0 atm and V₁ (Initial volume) = 12.0 L

So,

K_i = (1.0 atm) x (12.0 L)

K_i = 1.2 x 10¹​​​​​​​

Similarly,

P₂V₂ = K_f ....................(1)

Where, K_f is final constant of proportionality

Substitute the value of P₂ (Final pressure) = 2.0 atm and V₂ (Final volume) = 6.0 L

So,

K_f = (2.0 atm) x (6.0 L)

K_f = 1.2 x 10¹

Since,

K_i = K_f = 1.2 x 10¹​​​​​​​

This proves Boyle's law.