Chapter 3, Problem 3.FE

Interpretation Introduction

Interpretation:

The molecular mass and its uncertainty, the percent relative uncertainty in molecular mass for ${\text{NH}}_{\text{3}}$ has to be computed.

Concept Introduction:

Uncertainty:

Uncertainty means state of not certain in predicting a value.  In a measured value, the last digit will have associated uncertainty. Uncertainty has two values, absolute uncertainty and relative uncertainty.

Absolute uncertainty:

Expressed the marginal value associated with a measurement

Relative uncertainty:

Compares the size of absolute uncertainty with the size of its associated measurement

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

For Example:

Consider a burette reading as $\text{12}\text{.35}\pm \text{0}\text{.02 mL}$.

The absolute uncertainty is $0.02\text{ mL}$

The relative uncertainty is calculated using the formula,

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

Percent relative uncertainty:

$\text{Percent relative uncertainty = 100 }\times \text{ relative uncertainty}$