Using the equation 2h2+o2=2h2o, when 47g of water are produced, how many grams of hydrogen must react?

See , from the equation we can see that for forming two mole of H2O 2Mole of H2 has to react.

Mass of 2 Mole H2O is 18*2gm or 36gm.

So for forming 36 gm H2O 2×2 I.e. 4 gm H2 has to take part in reaction.

Therefore, to form 1 gm H2O 4÷36 gm of H2 has to take part.

So, for forming 47gm H2O (4÷36)×47 gm H2 has to take part

I.e. 5.22 gm of H2 has to take part

So, ans is 5.22 gm of hydrogen.

Hope it helps!!!

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