Acetonitrile (CH₃CN) is a polar organic solvent that dissolves a wide range of solutes, including many salts. The density of a 1.80 M LiBr solution in acetonitrile is 0.826 g/cm³. Calculate the concentration of the solution in (c) mass percentage of CH₃CN.

검증된 단계별 안내

First, understand that mass percentage is calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100%. In this case, we need to find the mass percentage of CH3CN in the solution.

Calculate the molar mass of LiBr. Lithium (Li) has an atomic mass of approximately 6.94 g/mol, and bromine (Br) has an atomic mass of approximately 79.90 g/mol. Add these values to find the molar mass of LiBr.

Use the molarity of the solution to find the mass of LiBr in 1 liter of solution. Since the solution is 1.80 M, this means there are 1.80 moles of LiBr per liter. Multiply the number of moles by the molar mass of LiBr to find the mass of LiBr in grams.

Calculate the total mass of the solution. Use the density of the solution (0.826 g/cm³) to find the mass of 1 liter of solution. Since 1 liter is 1000 cm³, multiply the density by 1000 cm³ to find the total mass of the solution in grams.

Subtract the mass of LiBr from the total mass of the solution to find the mass of CH3CN. Then, calculate the mass percentage of CH3CN by dividing the mass of CH3CN by the total mass of the solution and multiplying by 100%.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Molarity and Concentration

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. In this case, a 1.80 M LiBr solution indicates that there are 1.80 moles of lithium bromide dissolved in one liter of acetonitrile. Understanding molarity is essential for converting between moles and mass when calculating mass percentages.

Mass Percentage

Mass percentage is a way to express the concentration of a component in a mixture, calculated as the mass of the component divided by the total mass of the solution, multiplied by 100. To find the mass percentage of acetonitrile in the solution, one must determine the mass of acetonitrile and the total mass of the solution, which includes both the solute and the solvent.

Density and Volume Relationships

Density is defined as mass per unit volume (g/cm³). In this problem, the density of the solution allows for the conversion between mass and volume. By knowing the density of the 1.80 M LiBr solution, one can calculate the total mass of the solution, which is necessary for determining the mass percentage of acetonitrile.

Acetonitrile (CH3CN) is a polar organic solvent that dissolves a wide range of solutes, including many salts. The density of a 1.80 M LiBr solution in acetonitrile is 0.826 g/cm3. Calculate the concentration of the solution in (c) mass percentage of CH3CN.