Step-by-step explanation:
The relative formula mass of sodium carbonate decahydrate, Na2CO3.10H2O, can be calculated by adding the relative atomic masses of all the atoms present in one formula unit of the compound.
The formula unit of sodium carbonate decahydrate contains 2 sodium atoms (Na), 1 carbonate ion (CO3), and 10 water molecules (H2O).
The relative atomic mass of sodium (Na) is 22.99, carbon (C) is 12.01, oxygen (O) is 16.00, and hydrogen (H) is 1.01.
Therefore, the relative formula mass of sodium carbonate decahydrate is:
[2Na + CO3 + 10(H2O)]
[2 x 22.99 + 12.01 + 10(2 x 1.01 + 16.00)]
[45.98 + 12.01 + 180.20]
= 238.19
Therefore, the relative formula mass of sodium carbonate decahydrate is approximately 238.19.