M+ is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCl, in enough water to m

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2 months ago

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M+ is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCl, in enough water to m

ake 100.0 mL of solution. The student then mixes the solution with excess AgNO3 solution, causing AgCl to precipitate. The student collects the precipitate by filtration, dries, it and records the data shown below. (The molar mass of AgCl is 143 g/mol.) Mass of unknown chloride, MCl Mass of filter paper Mass of filter paper plus AgCl ppt 0.42 g 1.00 g 2.43 g Find the identity of metal chloride.
(A) lithium chloride
(B) sodium chloride
(C) magnesium chloride

Biology

2 answers:

lana [2.4K] · Answer 1 · 2026-03-23T14:07:13+03:00

Mass of AgCl = (mass of filter paper plus AgCl) - (mass of filter paper)
Mass of AgCl = 2.43 g - 1.00 g = 1.43 g AgCl

1.43 g AgCl (1 mole AgCl / 143 g AgCl) = 0.010 moles Ag left

Due to the 1:1 ratio of the ions, moles of Ag+ = moles of AgCl = 0.010 and moles of Cl- = moles of AgCl = 0.010. 

The formula for the unknown chloride is MCl, therefore:

0.010 moles Cl- (1 mole M+ / 1 mole Cl-) = 0.010 moles M+ 

0.010 moles Cl- (35.5 g Cl- / 1 mole Cl-) = 0.37 g Cl- 

Mass of M+ = mass of MCl - mass of Cl- = 0.42 g - 0.37 g = 0.05 g. 

0.05 g M+ / 0.010 moles M+ = 5 g/mole

I would conclude that option A is the most suitable answer. The metal chloride should be lithium chloride as its atomic mass is similar to the calculated mass derived above.

enyata [2.5K] · Answer 2 · 2026-03-23T14:08:54+03:00

It appears that one answer choice is missing. This question resembles one on my AP Chemistry practice test, where KCl would be the correct answer.

mass of AgCl = 2.23 - 0.80 = 1.43g AgCl

1.43g AgCl / 143g/mol AgCl = 0.01 moles AgCl

- The ratio of AgCl is 1:1, so:

moles of Ag+ = moles of Cl-, hence Ag+ has 0.01 moles and Cl- also has 0.01 moles

- MCl maintains the 1:1 ratio

moles of Cl- = moles of M+

- 0.01 moles of M+ and Cl-

0.01 Cl- = x/35.45 = 0.3545g Cl-

mass of MCl = 0.74g

0.74g MCl - 0.3545g Cl- = 0.3955g M+

0.3955g M+/x =0.010 mol M+

x= 39.55g M+

K+ has an approximate molar mass of 39.10

Thus, KCl is your answer