Chapter 11, Problem 11.67P

Interpretation Introduction

Interpretation:

Whether weight of rusted bar increases, decreases or equal to original bar has to be determined. Also, whether weight of bar increases, decrease or equal to original bar after the rust is scraped off has to be determined.

Concept Introduction:

Mole is S.I. unit. The number of moles is calculated as ratio of mass of compound to molar mass of compound.

Molar mass is sum of the total mass in grams of all atoms that make up mole of particular molecule that is mass of 1 mole of compound. The S.I unit is $\text{g/mol}$.

The expression to relate number of moles, mass and molar mass of compound is as follows:

  $\text{Number of moles}=\frac{\text{mass of the compound}}{\text{molar mass of the compound}}$

Mass percent is calculated by the mass of the element divided by the mass of compound and multiplied by 100.

The formula to calculate mass percentage of substance is as follows:

  $\text{Mass \% of substance}=\left(\frac{\text{Mass of substance}}{\text{Mass of compound}}\right)\left(100\right)$