Calcium hydride, cah2, reacts with water to form hydrogen gas:
cah2(s)+2h2o(l)→ca(oh)2(aq)+2h2(g)
this reaction is sometimes used to inflate life rafts, weather balloons, and the like, where a simple, compact means of generating h2 is desired.

how many grams of cah2 are needed to generate 145 l of h2 gas if the pressure of h2 is 823 torr at 21 ∘c?

Explanation:

To solve this problem, we can use the Ideal Gas Law:

pV = nRT

1. Collect the data in one place:

M_r:   42.09

           CaH₂ +2H₂O ⟶ Ca(OH)₂ +2H₂

p = 823 torr; V = 145 L; T = 21 °C

2. Convert temperature to kelvins

T = (21 +273.15) K = 294.15 K

3. Convert torrs to atmospheres.

4 Calculate the moles of H₂.

5. Calculate the moles of CaH₂

6. Calculate the mass of CaH₂

answer: gold foil experiment - he shot alpha particles at a gold foil

explanation: