Molality (m) - The number of moles of solute dissolved in 1000 gm (1kg) of solvent is called the Molality of solution.
It is represented by m.
The unit of molality is mole per kg solvent.
The value of molality is not affected by temperature.
Molality = moles of solute/mass of solvent (kg)
1m NaCl solution means that 1 mole of NaCl is dissolved in 1kg (1000gm) of water. Or 58.5 gm NaCl is dissolved in Ikg of water.
The effect of temperature - (i) Molality (m), Mass Percentage (%w/w), Part Per Million (ppm), Mole Fraction (X) etc. is not affected by temperature change.
(ii) Molarity (M), Normality (N), Volume Percentage (% v/v), Mass-Volume Percentage (% w/v) Formality (F) etc are affected by temperature.
Their values decrease with increasing temperature.