Question

Calculate the number of molecules in 1500 mL of a gas measured under a pressure of 800.0

torr at 19.0°C

Answer 1

3.97 x 10²² molecules

Step-by-step explanation:

To find the moles, you need to use the Ideal Gas Law:

PV = nRT

In this equation,

-----> P = pressure (atm)

-----> V = volume (L)

-----> n = moles

-----> R = Ideal Gas constant (0.08206 atm*L/mol*K)

-----> T = temperature (K)

Before you can plug the values into the equation, you need to (1) convert the pressure from torr to atm (by dividing by 760), then (2) convert the volume from mL to L (by dividing by 1000), and then (3) convert the temperature from Celsius to Kelvin (by adding 273).

P = 800.0 torr / 760 = 1.05 atm R = 0.08206 atm*L/mol*K

V = 1500 mL / 1000 = 1.5 L T = 19.0 °C + 273 = 292 K

n = ? moles

PV = nRT

(1.05 atm)(1.5 L) = n(0.08206 atm*L/mol*K)(292 K)

1.579 = n(23.96)

0.0659 = moles

Now, you need to convert moles to molecules using Avogadro's Number.

Avogadro's Number:

6.022 x 10²³ molecules = 1 mole

0.0659 moles 6.022 x 10²³ molecules
------------------------ x ------------------------------------- = 3.97 x 10²² molecules
1 mole