Calculation of Molecular Mass — lesson. Science State Board, Class 10.

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Calculate the gram molecular mass of the following compounds.

i. \(H_2O\)

ii. \(CO_2\)

iii. \((Ca)_3(PO_4)_2\)

\(H_2O\)

Data:

Atomic mass of \(H=1\)

Atomic mass of \(O=16\)

Solution:

\begin{array}{l} Gram molecular mass of H_{2} O \\ = (2 \times 1) + (1 \times 16) \\ = 2 + 16 \\ = 18 \end{array}

Hence, the gram molecular mass of \(H_2O=18\) \(g\).

ii.

\(CO_2\)

Data:

Atomic mass of \(C=12\)

Atomic mass of \(O=16\)

Solution:

\begin{array}{l} Gram molecular mass of {CO}_{2} \\ = (1 \times 12) + (2 \times 16) \\ = 12 + 32 \\ = 44 \end{array}

Hence, the gram molecular mass of \(CO_2=44\) \(g\).

iii.

\((Ca)_3(PO_4)_2\)

Data:

Atomic mass of \(Ca=40\)

Atomic mass of \(P=30\)

Atomic mass of \(O=16\)

Solution:

\begin{array}{l} Gram molecular mass of {Ca}_{3} {({PO}_{4})}_{2} \\ = (3 \times 40) + [30 + (4 \times 16)] \times 2 \\ = 120 + [30 + 64] \times 2 \\ = 120 + (94 \times 2) \\ = 308 \end{array}

Hence, the gram molecular mass of \((Ca)_3(PO_4)_2=308\) \(g\).

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8. Calculation of Molecular Mass