Solutions

Solutions

Question

Differentiate between molarity and molality values for a solution. What is the effect of change in temperature on molarity and molality values?

Answer

Molarity is defined as the number of moles of solute dissolved per litre of solution.

 Mathematically straight space straight M straight space equals straight space fraction numerator Number straight space of straight space moles straight space of straight space solute over denominator Volume straight space of straight space solution straight space in straight space litres straight space left parenthesis dm cubed right parenthesis end fraction

Molality of a solution is defined as the number of moles of solute dissolved in 1000 grams of solvent.

 Mathematically straight space straight m straight space equals straight space fraction numerator Number straight space of straight space moles straight space of straight space solute over denominator mass straight space straight o straight space solvent straight space in straight space kg end fraction

While molarity decreases with an increase in temperature, molality is independent of temperature. This happens because molality involves mass, which does not change with a change in temperature, while molarity involves volume, which is temperature dependent.

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