CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A crystalline mixture contains only NaCl and KCl. The total mass of the mixture is 12.00g, and the ratio of the mass of NaCl to the mass of KCl is experimentally determined to be 2.00:1.00. Molar masses are 58.44gmol−1 for NaCl and 74.55gmol−1 for KCl.
(a) Determine the individual masses of NaCl and KCl present in the sample.
(b) Calculate the amount of substance (in moles) of each salt contained in the mixture.
(c) Using your results from part (b), compute the average molar mass of the mixture to the appropriate number of significant figures.
(d) Qualitatively predict and justify how the average molar mass would change if the mass fraction of KCl were increased while the total sample mass remained constant.