You are in space and running out of water. You do have a great deal of magnesium carbonate pentahydrate. It is possible to extract the water from this. Determine the percent of water by mass in the hydrate magnesium carbonate pentahydrate (MgCO3·5H2O).

= 51.72%

Explanation: Use the formula

percentage by mass of water

= (molar mass of water / molar mass of MgCO3.5H2O) x 100

Molar mass of MgCO3.5H2O = 24+12 + (16X3) + [5 (2+16)

=36+48+90

=174g/mol

Molar mass of water 5H2O = 5 (2 + 16)

=5X18

=90

Therefore percentage of water = (90/174) x 100

= 51.72%

Note the molar masses: Mg = 24, C = 12, O = 16, H = 1