Answer:
a)0.981 atm
b)0.000787 moles of hydrogen gas.
c)25.4 g
d)4.5%
Explanation:
a) Partial pressure of hydrogen gas = total pressure of gas collected - pressure of water vapour
Partial pressure of hydrogen gas= 1.01 atm - 0.029 atm = 0.981 atm
Number of moles of hydrogen gas can be obtained from the ideal gas equation;
PV= nRT
P= pressure of dry hydrogen gas= 0.981 atm
V= volume of hydrogen gas= 19.6 ml or 0.0196 L
T= 24° + 273 = 297 K
R= 0.082 L.atm.K-1.mol-1
n= PV/RT= 0.981 × 0.0196 / 0.082 × 297
n= 0.0192/24.4
n= 0.000787 moles of hydrogen gas.
From the reaction equation;
1 mole of the metal yielded 1 mole of hydrogen gas hence 0.000787 moles of the metal will yield 0.000787 moles of hydrogen gas.
Molar mass of the metal is obtained from;
Number of moles = reacting mass / molar mass
Molar mass = reacting mass/ number of moles
Molar mass= 0.0200 g /0.000787 moles
Molar mass of metal= 25.4 g
% error in the molar mass of the metal = 25.4-24.3/24.3 × 100/1
% error in the molar mass of the metal = 4.5%
