Question

26. Which of the following concentration units will not change with temperature: molarity, percent mass, mole fraction, and molality. 27. Calculate the percent by mass of potassium nitrate in a solution made from 45.0 g KNO3 and 295 mL of water. The density of water is 0.997 g/mL. A) 1.51 % B) 7.57 % C) 13.3 % D) 15.2 % E) None of these 28. What is the molarity of a solution that is 5.50% by mass oxalic acid (C2H2O4) and has a density of 1.0244 g/mL? 29. The solubility of nitrogen gas at 25°C and a nitrogen pressure of 522 mmHg is 4.7 x 10 mol/L. What is the value of the Henry's Law constant in mol/L'atm? A) 6.8 x 10 mol/L atm B) 4.7 x 10 mol/L atm C) 3.2 x 10 mol/L atm D) 9.0 x 10 mol/L atm E) 1.5 x 10 mol/L atm 30. A solution is prepared by adding 40.3 g of Mg(NO3)2 to 127 g of water. Calculate the mole fraction and molality of magnesium nitrate in this solution.
help on questions 26-30

Answer 1

26. Concentration which involves mass and moles , don't change with temperature because mass and moles don't change with temperature.

While concentration unit involving volume , will change with temperature because volume changes with temperature .

Thus , as molarity = moles of solute/volume of solution in litres , includes volume . So molarity will change with temperature.

molality = moles of solute/mass of solvent in kg , includes moles and mass . So molality don't changes with temperature .

Percent mass = (mass of solute/mass of solution)×100 , involes mass only . So percent mass also don't changes with temperature.

Mole fraction = moles of solute/total moles of solution , involves only moles . So mole fraction also don't changes with temperature.