 Top

Molecular Weight Calculator
Top
The molecular weight of a substance expresses the relative mass of its molecule in composition to some arbitrarily selected standard. Molecular weight in chemistry is considered a simple matter being just the weight of one mole of the compound. The molecular weight of a substance is pure number having no unit.

$Molecular\ weight = \frac{Mass\ of\ 1\ molecule\ of\ the\ substance}{Mass\ of\ 1\ atom\ of\ hydrogen\ (H=1)}$
For a given known compound it is easily calculated as the sum of the atomic masses of the constituent atoms in the molecular formula.

Below is given a default molecular formula, you can just see how the molecular formula is calculated using the calculator.

## Steps for Molecular Weight Calculator

Step 1 :

Read the problem and find out the molecule whose molecular weight has to be determined.

Step 2 :

From the chemical formula of the given element the molecular weight can be calculated.

## Problems on Molecular Weight Calculator

1. ### The chemical formula for anhydrous codeine is C18H21NO3. Calculate the mass of 0.01 moles of the drug. [Data: m(C) = 12.01 gmol-1; m(H) = 1.008 gmol-1; m(N) = 14.01 gmol-1; m(O) = 16.00 gmol-1]

Step 1 :

First we determine the molecular molar mass from the chemical fomula.

Step 2 :

m(C18H21NO3) = 18 $\times$ 12.01 + 21 $\times$ 1.008 + 1 $\times$ 14.01 + 3 $\times$ 16.00

= 299.36 gmol-1

The molecular weight of C18H21NO3  = 299.36 gmol-1

2. ### Calculate the molecular weight of hexane.

Step 1 :

The chemical formula for hexane is C6H14.

Step 2 :

m(C6H14) = 6 $\times$ 12.01 + 14 $\times$ 1.008

= 86.175 gmol-1