Calcium hydride reacts with water to form calcium hydroxide and hydrogen gas. the balanced equation for this is cah2 + 2h2o > ca(oh)2 + 2h2 (a) how many grams of calcium hydride are needed to form 4.500 g of hydrogen?

If 4.5 g of Hydrogen is to be formed then this mass would have in x mol

x mol = Mass of H ÷  Molar Mass of H
         =  4.5g ÷ ( 1 x 2) g/mol
         = 2.25 mol

mole ratio of  CaH₂  :  H₂
                          1    :   2

∴ if mol of H₂ = 2.25 mol

then mol of CaH₂ = 2.25 mol × 
     
                             =  1.125 mol

Mass of CaH₂  =  1.125 mol  ×  [(40 × 1) + (2 × 1)]
                        =  47.25 g

Answer : option c) heat is released during the process.explanation :

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

  super sorry but i dont know lo