How many grams of water are needed to form 21.8 grams of oxygen gas?

24.5g

Explanation:

Given parameters:

Mass of oxygen gas = 21.8g

Unknown:

Mass of water  = ?

Solution:

This problem deals with the decomposition of water;

    Reaction equation;

                  2H₂O →  2H₂  +  O₂

2 mole of water will produce 1 mole of oxygen gas

First find the number of mole of the oxygen gas given;

          Number of moles  =

    molar mass of O₂   = 2(16) = 32g/mol

  Number of moles of O₂  =   = 0.68moles

    1 mole of oxygen gas will be produced from 2 mole of water

     0.68moles of oxygen gas will be produce from  0.68 x 2 moles of water;   = 1.36moles of water

Mass of water = number of moles x molar mass

  Molar mass of water = 2(1) + 16  = 18g/mol

Mass of water  = 1.36 x 18  = 24.5g

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: