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Chapter 12: Problem 13

Define the following concentration terms and give their units: percent by mass, mole fraction, molarity, molality. Compare their advantages and disadvantages.

Short Answer

Expert verified
Percent by mass is mass of solute/mass of solution x 100%, no units. Mole fraction is moles of component/total moles, no units. Molarity is moles of solute/liter of solution, unit is M. Molality is moles of solute/kg of solvent, unit is m. Percent by mass & Molality are ideal for temperature dependent calculations. Molarity & Mole fraction are best for volume or mole dependent situations.

Step by step solution

01

Define Percent by Mass & Its Units

Percent by mass (also known as weight percent or mass percent) is a way of expressing a concentration or a way of describing the composition of a mixture. It is defined as the mass of the solute divided by the mass of the solution, multiplied by 100. It's unitless since it's a percentage (g/g x 100%).
02

Define Mole Fraction & Its Units

Mole fraction is another method for expressing the concentration of a solution. It is the ratio of the number of moles of a component to the total number of moles in a mixture. It usually has no units because it's a ratio of the number of moles to the total number of moles.
03

Define Molarity & Its Units

Molarity is a concentration term that refers to the number of moles of a solute in 1 liter of solution. The unit of molarity is moles per liter (mol/L), often written as M.
04

Define Molality & Its Units

Molality is another concentration term used in chemistry. It refers to the number of moles of solute per kilogram of solvent. The unit of molality is moles per kilogram (mol/kg), often written as m.
05

Compare Advantages and Disadvantages

Percent by mass is easy to comprehend but it's not useful when it comes to temperature dependent calculations. Mole fraction is advantageous for gas calculations but it does not define the volume or mass of the solution. Molarity is commonly used, and it's easy to measure the volume of a solution, however, it changes with temperature. Lastly, molality is good for temperature dependent calculations as it depends only on the mass of the solvent, but it's more difficult to measure mass compared to volume.

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Most popular questions from this chapter

The vapor pressures of ethanol \(\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\right)\) and 1 -propanol \(\left(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{OH}\right)\) at \(35^{\circ} \mathrm{C}\) are \(100 \mathrm{mmHg}\) and \(37.6 \mathrm{mmHg},\) respectively. Assume ideal behavior and calculate the partial pressures of ethanol and 1-propanol at \(35^{\circ} \mathrm{C}\) over a solution of ethanol in 1-propanol, in which the mole fraction of ethanol is \(0.300 .\)

How does each of the following affect the solubility of an ionic compound? (a) lattice energy, (b) solvent (polar versus nonpolar), (c) enthalpies of hydration of cation and anion

Which of the following aqueous solutions has (a) the higher boiling point, (b) the higher freezing point, and (c) the lower vapor pressure: \(0.35 \mathrm{~m}\) \(\mathrm{CaCl}_{2}\) or \(0.90 \mathrm{~m}\) urea? Explain. Assume \(\mathrm{CaCl}_{2}\) to undergo complete dissociation.

Describe how hydrophilic and hydrophobic colloids are stabilized in water.

Ammonia \(\left(\mathrm{NH}_{3}\right)\) is very soluble in water, but nitrogen trichloride \(\left(\mathrm{NCl}_{3}\right)\) is not. Explain.
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