Calcium hydride reacts with water to form calcium hydroxide and hydrogen gas. How many grams of calcium hydride are needed to form 8.5 grams of hydrogen?

1 Answer
anor277
Mar 20, 2016

Approx. #85# #g# of calcium hydride are required

Explanation:

#CaH_2(s) + 2H_2O(l) rarr Ca(OH)_2(aq) + 2H_2(g)uarr#

The balanced equation gives a 1:1 stoichimetry between calcium hydride and dihydrogen gas, We need to (i) work out the molar quantity of dihydrogen, and (ii) convert this into an equivalent mas of #CaH_2#.

#"Moles of "H_2(g)# #=# #(8.5*g)/(2.0*g*mol^-1)# #~~# #4# #mol#.

So, if 4 mol of calcium hydride are required. This gives a mass of #2*molxx42.09*g*mol^-1" calcium hydride"# #=# #??g#

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