Lead compounds are often highly colored and are toxic to...

Lead compounds are often highly colored and are toxic to mold, mildew, and bacteria, properties that in the past were useful for paints used before 1960 . Today we know lead is very hazardous and it is not used in paint; however, old paint is still a problem. If a certain lead-based paint contains $14.5 \% \mathrm{PbCr}_{2} \mathrm{O}_{7}$ and $73 \%$ of the paint evaporates as it dries, what mass of lead will be in a paint chip that weighs $0.15 \mathrm{~g}$ ?

Key Concepts

Proportional Reasoning

Proportional reasoning is a mathematical approach to relate parts to the whole. In chemical calculations, it is used to scale percentages and ratios—for example, to adjust for the change in mass due to evaporation and to calculate the mass of an element present in a compound based on the originally given percentages.

Stoichiometry and Molar Mass Calculations

Stoichiometry in chemistry involves using the molar masses and the chemical formulas of compounds to deduce the mass or mole relationship between different elements. It is particularly important in determining the fraction of an element, like lead, in a compound by analyzing its contribution to the overall molar mass.

Volatile and Non?Volatile Components

This concept involves understanding that a mixture may contain components that evaporate (volatile) and those that remain (non?volatile) upon processes such as drying. Recognizing what fraction of the original mass remains is crucial for determining the amount of constituent substances in the residue after evaporation.

Percent Composition

Percent composition refers to the percentage by mass of each component in a mixture or compound. It allows you to determine how much of a given substance is present in a total mass by converting percentages into actual mass values, an essential step in many chemical calculations.

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