Question

Water is 11.2% by mass hydrogen (H). How many kilograms of water would contain 4.8 g of hydrogen?

Answer 1

We (i) simply determine the atomic quantity of hydrogen; and (ii) give a corresponding atomic quantity of water. We get an answer under 0.045 kg.

Explanation:

If there are 4.8 g of hydrogen in an unspecified quantity of water, there are `(4.8*g)/(1.00794*g*mol^-1)` `=` `4.76` `mol` `H`.

Given the composition of water, `H_2O`, there are thus `2.38` `mol` water.

Thus, mass of water `=` `2.38` `mol` `xx` `18.01` `g*mol^-1xx10^-3*kg*g^-1` `=` `??` `kg`