Answer:
The correct answer is 0.00582 grams.
Explanation:
In order to solve the question, let us consider the vapor pressure of H2O, as hydrogen gas is collected over water, therefore, we have to consider the vapor pressure of water in the given case. Let us assume that the pressure is 760 torr or 1 atm.
It is known that the vapor pressure of water at 40 degree C is 53.365 torr (Based on the data).
Therefore, the pressure of H2 will be,
P = 760-55.365 = 704.635 torr or 704.635/760 = 0.9272 atm
The volume of the hydrogen gas collected in the tube is 80 ml or 0.08 L
Temperature in Kelvin will be 40+273 = 313 K
To calculate the moles of hydrogen (H2) gas, there is a need to use the ideal gas equation, that is, PV= nRT, in this R is the gas constant, whose value is 0.0821 L atm/molK, and n is the moles of the gas.
By inserting the values in the equation we get:
PV = nRT
n = PV/RT = 0.9272 *0.08 / 0.0821 * 313
n = 0.00289 moles
The mass of H2 will be moles * molar mass = 0.00289 * 2.016
= 0.00582 grams.
