± Introduction to Units of Concentration mass %=mass of componenttotal mass of s

Question

± Introduction to Units of Concentration

mass %=mass of componenttotal mass of solution×100%

mole fraction (X)=moles of componenttotal moles of solution

molarity (M)=moles of soluteliters of solution

molality (m)=moles of solutemass of solvent (kg)

A solution was prepared by dissolving 35.0 g of KCl in 225 g of water.

Part A

Calculate the mass percent of KCl in the solution.

Express your answer with the appropriate units.

13.5 { m \%}

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Part B

Calculate the mole fraction of the ionic species KCl in the solution.

Express the concentration numerically as a mole fraction in decimal form.

.3758

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Part C

Calculate the molarity of KCl in the solution if the total volume of the solution is 239 mL.

Express your answer with the appropriate units.

1.96mol

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Part D

Calculate the molality of KCl in the solution.

Express your answer with the appropriate units.

± Introduction to Units of Concentration

The composition of a solution can be expressed in several different ways. Four of the most common concentration units are defined as follows:.

mass %=mass of componenttotal mass of solution×100%

mole fraction (X)=moles of componenttotal moles of solution

molarity (M)=moles of soluteliters of solution

molality (m)=moles of solutemass of solvent (kg)

A solution was prepared by dissolving 35.0 g of KCl in 225 g of water.

Part A

Calculate the mass percent of KCl in the solution.

Express your answer with the appropriate units.

13.5 { m \%}

SubmitHintsMy AnswersGive UpReview Part

Correct

Part B

Calculate the mole fraction of the ionic species KCl in the solution.

Express the concentration numerically as a mole fraction in decimal form.

X =

.3758

SubmitHintsMy AnswersGive UpReview Part

Incorrect; Try Again; 5 attempts remaining

Part C

Calculate the molarity of KCl in the solution if the total volume of the solution is 239 mL.

Express your answer with the appropriate units.

1.96mol

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Incorrect; Try Again; 5 attempts remaining

Part D

Calculate the molality of KCl in the solution.

Express your answer with the appropriate units.

Explanation / Answer

here

1)

mass percentage = (mass of KCl / total mass) x 100
mass percentage = (35.0 g / (35.0 + 225.0 g) x 100 = 13.5 %

mol fraction KCl = mole KCl / total moles
35.0 g KCl x (1 mol / 74.55 g) = 0.469 mol KCl
225 g H2O x (1 mol / 18.0 g) = 12.5 mol H2O
Total mol = 0.469 + 12.5 = 13.0 mol (sig figs to .1)
mol fraction KCl = 0.469 / 13.0

mol fraction KCl= 0.0361

c)

M = mol / L = 0.469 mol / 0.239 L = 1.96 M

D)

molality = mol KCl / kg H2O
molality = 0.469 mol / 0.225 kg H2O = 2.08 molal

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