3 is C i believe, and as for 4 minerals are solid, natural.. that's about all I can say...
The reaction is
CaC₂(s) + 2H₂O (l) -----> Ca(OH)₂ (s) + C₂H₂ (g)
As we have data of gas ethyne (or acetylene), C₂H₂
We can calculate the moles of acetylene and from this we can estimate the mass of calcium carbide taken
the moles of acetylene will be calculated using ideal gas equation
PV =nRT
R = gas constant = 0.0821 Latm/molK
T = 385 K
V = volume = 550 L
P = Pressure = 1.25 atm
n = moles = ?
n = PV /RT = 1.25 X 550 / 0.0821 X 385 = 21.75 mol
As per balanced equation these moles of acetylene will be obtained from same moles of calcium carbide
moles of calcium carbide = 21.75mol
molar mass of CaC₂ = 40 + 24 = 64
mass of CaC₂ = moles X molar mass = 21.75 X 64 = 1392g
Answer: 873 kJ of energy will be required to break two moles of hydrogen gas.

Above chemical equation shows that two moles of hydrogen gas is reacting with one mole of oxygen gas to give two mole of water molecule.
Bond energy of H-H = 436kJ
According to reaction we have two moles hydrogen,so energy required to break the
H-H bond in two moles of hydrogen gas will be:

= 872kJ
872kJ of energy will be required to break H-H bond in two moles of hydrogen gas.