You analyze a sample of unknown metal as you would in this experiment. You measure the volume of H2(g) generated to be 71.85 mL and the water temperature to be 20.0°C. You calculate PH2 to be 0.781 atm. Use the ideal gas law to calculate the number of moles of hydrogen gas generated.

The number of moles of hydrogen gas generated is

Explanation:

To calculate the number of moles of hydrogen gas, we use the equation given by ideal gas which follows:

where,

P = pressure of the gas = 0.781 atm

V = Volume of the gas = 71.85 mL = 0.07185 L     (Conversion factor:  1 L = 1000 mL)

T = Temperature of the gas =

R = Gas constant =

n = number of moles of hydrogen gas = ?

Putting values in above equation, we get:

Hence, the number of moles of hydrogen gas generated is

the correct answer is:

a. formation of precipitation