 ## General Chemistry

Learn the toughest concepts covered in Chemistry with step-by-step video tutorials and practice problems by world-class tutors

14. Solutions

# Molality

Molality (m) represents the number of moles of solute dissolved per kilogram of solvent.

Understanding Molality
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concept

## Molality Concept 1 40s
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now morality, which is symbolized by lower Case M, is another way to express solution concentration and is temperature independent. Now. The reason for this is that the units for morality don't involve volume, and as a result it's not going to be affected by increases or decreases in temperature. Now we're going to say that morality represents the number of moles of solute per kilogram of solvent. So here, morality or case them equals moles of solute over kilograms of solvent. So this is the formula you need to memorize when it comes to the idea of morality.
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example

## Molality Example 1 2m
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A solution contains 24.8 g of sucrose, which has the molecular formula of C- 12, H- 22011 and it's dissolved in 550 g of water. Calculate the morality of the solution. So remember Malala t equals moles of solute divided by kilograms of solvent. Our salute is the amount that's smaller, so 24.8 g of sucrose would be our salute and then the larger amount would be our solvent. So water here is a solvent. So what I'm gonna do first is the easier one. Let's just convert grams to kilograms. So we have here 550 g of water And remember, one kg is 10 to the three. So one kg is tender, the three grants So that's .550 kg. Next, I need to find the moles of sucrose. So we have 2. 48, or 24.8 grams of sucrose For every one mole of sucrose. How many grams do we have? So we have 12 carbons. 22 hydrogen, 11 oxygen's. Their combined mass comes out to 3. 42.296 So here, grams, cancel out and we'll have our moles, which comes out to be 0.7245 moles. I'm gonna take those moles and plug them up over here. Moles of sucrose So when I divide my moles by my kilograms, I'll get my morality. So here, 24.8 has three sig figs 550.0 Has four sick fix always go with the least number of sick fix. So we're gonna have three sick fix at the end. So this comes out to the point 132 mobile, so this would be our final answer.
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Problem

A solution is prepared by dissolving 43.0 g potassium chlorate, KClO3, in enough water to make 100.0 mL of solution. If the density of the solution is 1.760 g/mL, what is the molality of KClO3 in the solution?

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Problem

The density of a 15.7 M methanol (CH3OH) solution is 0.858 g/mL. If H2O is the solvent, what is the molality of the solution?

Osmolality
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concept

## Molality Concept 2 1m
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Oz. Morality, also called ionic morality, represents the number of dissolved particles in a solution. And we're going to say that when it comes to Covalin compounds, the number of ions that they have is just one. Here. They don't break up into multiple particles or ions. We just keep them together as one molecule. So for them, it equals one. Now. The osmolarity formula is that Oz morality equals the number of ions, times the morality of our solution and or compound. The way we approach this is we break up ionic compounds into ions, and we count the total number of ions and multiply Beaumont Reality of solution. So if we take a look here, we have 2.5 moral of sodium chloride. Sodium chloride is an ionic compound that breaks up into two ions sodium ion and chloride ions. That's a total number of two ions. So we're going to say here that the osmolarity equals two because there's two ions times the morality of our solution. So again, it's 2.5 mole of sodium chloride solution. That would mean that our Total Ionic morality here would be five mol. So that's the approach you need to take when it comes to Ionic morality, otherwise known as Osmolarity.

Osmolality or Ionic Molality, represents number of dissolved particles in a solution.

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example

## Molality Example 2 1m
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