Calculate the number of moles and the mass of the solute in...

Calculate the number of moles and the mass of the solute in each of the following solutions: (a) 325 $\mathrm{mL}$ of $8.23 \times 10^{-5} \mathrm{M} \mathrm{KI}$ , a source of iodine in the diet (b) 75.0 $\mathrm{mL}$ of $2.2 \times 10^{-5} \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4},$ a sample of acid rain (c) 0.2500 $\mathrm{L}$ of $0.1135 \mathrm{M} \mathrm{K}_{2} \mathrm{CrO}_{4},$ an analytical reagent used in iron assays (d) 10.5 $\mathrm{L}$ of $3.716 \mathrm{M}\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4},$ a liquid fertilizer

Calculate the number of moles and the mass of the solute in each of the following solutions:
(a) 325 $\mathrm{mL}$ of $8.23 \times 10^{-5} \mathrm{M} \mathrm{KI}$ , a source of iodine in the diet
(b) 75.0 $\mathrm{mL}$ of $2.2 \times 10^{-5} \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4},$ a sample of acid rain
(c) 0.2500 $\mathrm{L}$ of $0.1135 \mathrm{M} \mathrm{K}_{2} \mathrm{CrO}_{4},$ an analytical reagent used in iron assays
(d) 10.5 $\mathrm{L}$ of $3.716 \mathrm{M}\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4},$ a liquid fertilizer

Key Concepts

Molarity

Molarity is a concentration unit defined as the number of moles of solute per liter of solution. It provides a direct relationship between the amount of solute and the volume of the solution, making it essential for preparing and diluting solutions in the laboratory.

Volume Conversion

Volume conversion is crucial when working with solutions because the volume provided may be in units such as milliliters, and it must be converted to liters (the SI unit for volume) to be compatible with the molarity formula. This ensures accurate calculations of the amount of solute present.

Moles Calculation

The calculation of moles from molarity involves multiplying the molarity (moles per liter) by the volume of the solution in liters. This step is fundamental in determining the amount of substance within a given solution, enabling further stoichiometric calculations.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole. It is determined by summing the atomic masses of the constituent elements and is used to convert between moles and grams, linking the microscopic scale of atoms and molecules to macroscopic measurements.

Mass Calculation from Moles

The mass of a solute in a solution is calculated by multiplying the number of moles of the solute by its molar mass. This conversion is key in quantitative chemistry for preparing solutions, responding to changes, and analyzing the composition of substances.

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