Question

How many moles of gas are present when you collect 35.83 mL of the gas over water at 25.3°C and 0.97 atm?

Answer 1

Answer is: 0.00142 moles of gas are present.

Ideal gas law: p·V = n·R·T.

p = 0.97 atm.; pressure of the gas.

T = 25.3 + 273.15.

T = 298.45 K; temperature of the gas.

V = 35.83 mL ÷ 1000mL/L.

V = 0.03583 L; volume of the gas.

R = 0.08206 L·atm/mol·K; gas constant.

n = 0.97 atm · 0.03583 L ÷ (0.08206 L·atm/mol·K · 298.45 K).

n = 0.00142 mol; amount of the gas.

Answer 2

Use Ideal Gas equation since values are given in Pressure (P), Volume (V), Temperature (T). 
                                 P V = n R T ; n= PV / RT
You can't use 1 mole= 22.4 L equation. Temperature and pressure values are not standard. ( 1 atm, 0 

To choose the value of R ( gas constant), check out the units of other values in the equation. They are in atm,liter, kelvin, and mole.  So, its value is 0.082 L atm/ K mol.

P= 0.97 atm
V= 35.83 * 10 ⁻³ L (conversion from ml to,  just multiplied by 10 ⁻³ )
R= 0.082 L atm/ K mol
T= (25.3 + 273) K ( recall Kelvin = Celcius + 273; K= °C + 273)

Substitute values into equation of  n= PV / RT

n= (0.97 atm) (35.83 * 10 ⁻³ L) /  (0.082 L atm/ K mol) (298.3 K)= 0.014 mole

The answer is 0.014 mole