Question

Calculate the relative molecular mass of CuSO4.5H20

Answer 1

Answer:

Molar mass of CuSO4.5H2O = 249.685 g/mol

Convert grams CuSO4.5H2O to moles  or  moles CuSO4.5H2O to grams

Molecular weight calculation:

63.546 + 32.065 + 15.9994*4 + 5*(1.00794*2 + 15.9994)

Percent composition by elementElement  Symbol  Atomic Mass  # of Atoms  Mass PercentCopperCu63.546125.450%HydrogenH1.00794104.037%OxygenO15.9994957.671%SulfurS32.065112

Answer 2

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Solution:

Relative molecular mass indicates molecular mass or molar mass of a compound

For CuSO4. 5H2O

1. We have to find molar mass of each element
2. Molar mass of Copper (Cu) = 63.5g
3. Molar mass of Sulphur (S) = 32 g
4. Molar mass of oxygen (O) = 16 g
5. Molar mass of hydrogen (H) = 1 g
6. If you find it difficult to calculate entire divide CuSO4. 5H2O into two parts that is CuSO4 and 5 H2O.
7. Find molar mass of CuSO4 and 5H2O separately and then add it

CuSO4= Molar mass of Cu + Molar mass

of S + 4 × Molar mass of O

CuSO4 = 63.5+32+4×16

CuSO4 = 63.5+32+64

CuSO4 = 159.5gm/mol

For 5H2O = 5 ×[ 2 × 1 + 16]

5H2O = 5×[18]

5H2O = 90 gm/mol

Solving for CuSO4. 5H2O together

CuSO4. 5H2O = 159.5+90 = 249.5 gm/mol

Required answer:

Therefore, relative molecular mass of CuSO4. 5 H2O = 249.5 gm/mol

We write the unit as gm/mol because

Mole = Mass/ Molar mass

Molar mass = Mass / Mole

Molar mass = gram/ mole

Additional Points:

1. If the molecular formula is given as 5H2O it means there are 10 H and 5 O. So while solving for molar mass we can directly write it as 10 × molar mass of H+ 5× molar mass of Oxygen
2. Try to remember molar mass of certain elements to solve easily
3. Solve more such questions to get a good hold on it.