A 0.6753 g sample of an unknown metal was
converted to the nitrate, MCl2, then a solution of the
nitrate was treated with silver nitrate to give
MCl2 (aq) + 2 AgNO3 → M(NO3)2 + 2 AgCl(s)
silver chloride crystals. The silver chloride was
isolated and weighed 1.7220 g. What was the metal?
I've have worked it out and gotten 41.55 whcih is Ca, but the prof says the correct answer is Cd, which is 112.41.
The story you tell of the metal is not very good; somehow the nitrate and chloride became mixed up. At any rate
M --> M(NO3)2--> MCl2 --> 2AgCl
mols AgCl = 1.722/143.3209 = 0.01201.
moles M = 1/2 that.
0.01201/2 = 0.006 but you need to do it more accurately.
molar mass = grams/mol = 0.6753/0006 = about 112
To determine the identity of the metal, we need to use the given information. Let's break down the steps involved in solving this problem:
1. Start with the mass of the silver chloride produced, which is 1.7220 g.
2. Apply the stoichiometry of the balanced chemical equation. According to the equation, 2 moles of silver chloride (AgCl) are produced from 1 mole of MCl2.
3. Convert the grams of silver chloride to moles by dividing the mass by the molar mass of AgCl. The molar mass of AgCl is calculated by adding the atomic masses of silver (Ag) and chlorine (Cl), which gives us 143.32 g/mol.
Moles of AgCl = mass of AgCl / molar mass of AgCl
= 1.7220 g / 143.32 g/mol
≈ 0.012 g/mol
4. According to the balanced chemical equation, 2 moles of silver chloride correspond to 1 mole of MCl2. Therefore, the moles of MCl2 can be calculated by dividing the moles of AgCl by 2.
Moles of MCl2 = 0.012 g/mol / 2
= 0.006 mol
5. Now, determine the molar mass of the unknown metal (M) by dividing the mass of the unknown sample (0.6753 g) by the moles of MCl2.
Molar mass of M = mass of sample / moles of MCl2
= 0.6753 g / 0.006 mol
= 112.55 g/mol (rounded to four decimal places)
Based on the calculation, the molar mass of the metal is approximately 112.55 g/mol. This matches the molar mass of cadmium (Cd), which is 112.41 g/mol. Therefore, the correct answer is Cd, not Ca.
It's possible that you made a calculation error or used incorrect molar masses for calcium (Ca) and cadmium (Cd). Double-check your calculations and ensure you are using the accurate molar masses from the periodic table.