If the atmospheric pressure in the laboratory is 1.2 atm, how many moles of gas were in each syringe?

air(h2o) syringe
room temperature water at 21.3 degrees celsius
volume of 5.1 ml

hydrogen(h2) syringe
room temperature water at 21.3 degrees celsius
volume of 5.2 ml

A: 2.525 x 10⁻⁴ mol

B: 2.583 x 10⁻⁴ mol

Explanation:

Part A:

Data Given:

Convert Temperature to Kelvin

T = °C + 273

T = 21.3 + 273 = 294.3 K

Convert mL to liter

1000 mL = 1 L

5.1 ml = 5.1/1000 = 0.0051 L

Solution

no. of moles can be calculated by using ideal gas formula

                         PV = nRT

Rearrange the equation for no. of moles

                          n= PV / RT . . . . . . . . . (1)

where

P = pressure

V = Volume

T= Temperature

n = Number of moles

R = ideal gas constant

where

R = 0.08206 L.atm / mol. K

Now put the value in formula (1) to calculate no. of moles of

              n = 1.2 atm x 0.0051 L / 0.08206 L.atm.mol⁻¹. K⁻¹ x 294.3 K

              n = 0.0061 atm.L / 24.162 L.atm.mol⁻¹

              n = 2.525 x 10⁻⁴ mol

no. of moles of gas (H₂O) = 2.525 x 10⁻⁴ mol

Part B:

Data Given:

Convert Temperature to Kelvin

T = °C + 273

T = 21.3 + 273 = 294.3 K

Convert mL to liter

1000 mL = 1 L

5.2 ml = 5.2/1000 = 0.0052 L

Solution

no. of moles can be calculated by using ideal gas formula

                         PV = nRT

Rearrange the equation for no. of moles

                         n= PV / RT . . . . . . . . . (1)

where

P = pressure

V = Volume

T= Temperature

n = Number of moles

R = ideal gas constant

where

R = 0.08206 L.atm / mol. K

Now put the value in formula (1) to calculate no. of moles of

              n = 1.2 atm x 0.0052 L / 0.08206 L.atm.mol⁻¹. K⁻¹ x 294.3 K

              n = 0.0062 atm.L / 24.162 L.atm.mol⁻¹

              n = 2.583 x 10⁻⁴ mol

no. of moles of gas (H₂) = 2.583 x 10⁻⁴ mol

the answer is d. 74.02