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 (b) mole fraction of LiBr,

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insert step 1> Calculate the molar mass of LiBr by adding the atomic masses of lithium (Li) and bromine (Br).

insert step 2> Use the molarity (1.80 M) to find the moles of LiBr in 1 liter of solution.

insert step 3> Calculate the mass of 1 liter of the solution using its density (0.826 g/cm^3). Remember that 1 liter is equivalent to 1000 cm^3.

insert step 4> Determine the mass of acetonitrile in the solution by subtracting the mass of LiBr (from step 2) from the total mass of the solution (from step 3).

insert step 5> Calculate the mole fraction of LiBr by dividing the moles of LiBr by the total moles of all components in the solution (moles of LiBr and moles of acetonitrile).

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주요 개념

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

Molarity

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. In this case, the 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 different concentration units and for calculations involving solutions.

Mole Fraction

Mole fraction is a way to express the concentration of a component in a mixture, defined as the ratio of the number of moles of that component to the total number of moles of all components in the mixture. To calculate the mole fraction of LiBr in the solution, one must determine the moles of LiBr and the moles of acetonitrile, which requires knowledge of the solution's density and volume.

Density

Density is defined as mass per unit volume and is crucial for converting between mass and volume in solution calculations. The density of the LiBr solution (0.826 g/cm³) allows us to find the mass of the solution, which can then be used to calculate the number of moles of the solvent and solute. This information is vital for determining the mole fraction of LiBr.

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 (b) mole fraction of LiBr,