Respuesta :
Answer:
2.144 g of calcium hydride are needed to produce 2.5 l of hydrogen gas, collected over water at 26 degrees celcius and 760 torr.
Explanation:
The reaction of Calcium hydride and water is given by
CaH₂ + 2H₂O -----> Ca(OH)₂ + 2H₂
2 moles of Hydrogen gas are produced from 1 mole of Calcium hydride.
But we need to find out how much moles of Hydrogen are produced from this reaction first.
Using the ideal gas, equation,
PV = nRT
P = pressure = 760 torr = 101325 Pa
V = volume of hydrogen gas produced = 2.5 L = 0.0025 m³
n = number of moles of Hydrogen gas produced = ?
R = molar gas constant = 8.314 J/mol.K
T = absolute temperature in Kelvin = 26°C = 299.15 K
n = PV/RT = (101325×0.0025)/(8.314×299.15) = 0.102 moles
Back to the stoichiometric balance of the reaction
CaH₂ + 2H₂O -----> Ca(OH)₂ + 2H₂
2 moles of Hydrogen are produced from 1 mole of Calcium hydride
0.102 moles of Hydrogen will be produced from (0.102 × 1/2) moles of Calcium hydride.
Moles of Calcium hydride = 0.051 moles.
Mass of Calcium hydride that reacted = number of moles of Calcium hydride that reacted × Molar mass
Moles mass of Calcium hydride = 42.094 g/mol
Mass of Calcium hydride that reacted = 0.051 × 42.094 = 2.144g
