Question

Compute the molecular mass and its uncertainty for ${\mathbf{NH}}_{\mathbf{3}}$. What is the percent relative uncertainty in molecular mass?

Short answer

The percent relative uncertainty is$100\times \mathrm{relative}\mathrm{uncertainty}$

Step-by-step solution

Step 1:The introduction of interpretation, uncertainty and absolute uncertainty

Interpretation:

For ${\mathrm{NH}}_3$, the molecular mass and its uncertainty, as well as the percent relative uncertainty in molecular mass, must be computed.

Uncertainty:

Uncertainty refers to the inability to predict a value. The last digit in a measured value will have related uncertainty. Absolute and relative uncertainty are two types of uncertainty.

Absolute uncertainty:

The marginal value associated with a measurement is expressed as absolute uncertainty.

The value of percent relative uncertainty

The relative uncertainty is:

Compares the extent of absolute uncertainty to the size of the measurement it is connected with.

$\mathrm{Relative}\mathrm{uncertainty}=\frac{\mathrm{absolute}\mathrm{uncertainty}}{\mathrm{magnitude}\mathrm{of}\mathrm{measurement}}$

As a example it can be taken that:

Consider the following burette reading: $12.35\pm 0.02\mathrm{mL}$.

is the absolute uncertainty.

The formula is used to calculate the relative uncertainty is:

$\mathrm{Relative}\mathrm{uncertainty}=\frac{\mathrm{absolute}\mathrm{uncertainty}}{\mathrm{magnitude}\mathrm{of}\mathrm{measurement}}$

So,the percent relative uncertainty is:

$Percentrelativeuncertainty=100\times relativeuncertainty$

The percent relative uncertainty is$100\times relativeuncertainty$