Comparing Molality & Molarity: Which is More Concentrated?

In summary, different substances will have different molarities and molalities depending on the solvent and solvent/substance combination.
  • #1
Garvit Goel
13
0
hello,
i had been comparing the molarity and molality of a solution.
i know molarity is moles of solute per L of solution, and molality is moles of solute per kg of solvents.
but what i m interested to know is- which of the two is more concentrated- 1molal solution or 1 molar solution.
my chemistry teacher said molarity is more concentrated. but i think it depends on the density if solvent if they are ideal solution.
I would really appreciate any assistance regarding this issue.
 
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  • #2
It is not only a function of a solution density, but also substance molar mass. It it probably possibleto find pairs substance/solvent such that for one molarity is higher, for other molality is higher. Which means there is no one answer to the problem.
 
  • #3
Garvit Goel said:
hello,
i had been comparing the molarity and molality of a solution.
i know molarity is moles of solute per L of solution, and molality is moles of solute per kg of solvents.
but what i m interested to know is- which of the two is more concentrated- 1molal solution or 1 molar solution.
my chemistry teacher said molarity is more concentrated. but i think it depends on the density if solvent if they are ideal solution.
I would really appreciate any assistance regarding this issue.

What do you mean by more concentrated? Do you mean, "if you convert a concentration of (1 mol solute)/(1 kg solvent) into molarity, is it higher or lower than 1 M?"

If that is what you are asking, then there is no way to answer the question. This is because different solute/solvent combinations result in solutions with different densities .. stated more specifically, we say that different solutes have different partial molar volumes. [EDIT: To clarify, this means that if you add a certain volume of solute to a certain volume of solvent, the volume of the resulting solution is NOT simply the sum of the two starting volumes.] To make it even more complicated, partial molar volumes depend on how much solute is added.
 
Last edited:

1. What is the difference between molality and molarity?

Molality and molarity are both units of concentration used in chemistry. Molality (m) is defined as the number of moles of solute per kilogram of solvent, while molarity (M) is defined as the number of moles of solute per liter of solution. In other words, molality takes into account the mass of the solvent, while molarity takes into account the volume of the solution.

2. Which unit of concentration is more accurate?

Both molality and molarity have their own advantages and are used in different situations. Molality is more accurate when dealing with solutions at different temperatures because it is not affected by changes in volume due to temperature. On the other hand, molarity is more commonly used and easier to measure in the laboratory.

3. How do you convert between molality and molarity?

To convert from molality to molarity, you need to know the density of the solution. You can use the formula M = m / (1 + (mM*d)), where M is molarity, m is molality, and d is density. To convert from molarity to molality, you need to know the molecular weight of the solute. You can use the formula m = M * (MW / d), where m is molality, M is molarity, MW is molecular weight, and d is density.

4. Which unit of concentration is more commonly used in industry?

Molality is more commonly used in industry because it is not affected by temperature changes, making it more accurate for industrial processes. However, molarity is still widely used in the laboratory and in academic settings.

5. Can you have the same numerical value for molality and molarity?

No, you cannot have the same numerical value for molality and molarity. This is because they are calculated using different units (mass for molality and volume for molarity) and take into account different factors (mass of solvent for molality and volume of solution for molarity).

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