Respuesta :
Answer:
M is cobalt (Co)
Explanation:
Step 1: Data given
Mass of MCl2(H2O)6 = 2.9237 grams
After completely drying the sample (which means removing the 6 moles of H2O per mole of MCl2), the sample weighs 1.5941 g.
Step 2: Calculate mass of water
Mass of water = 2.9237 - 1.5941 = 1.3296 grams
Step 3: Calculate moles water
Moles water = mass water / molar mass water
Moles water = 1.3296 grams / 18.02 g/mol
Moles water = 0.07378 moles
Step 4: Calculate moles of the whole substance
For 1 mol MCl2(H2O)6 we have 6 moles H2O
Number of moles of the whole substance = 0.07378 / 6 = 0.01230 moles
Step 5: Calculate molar weight of the substance
Molar weight = mass / moles
Molar weight = 1.5941 grams / 0.01230 moles
Molar weight = 129.6 g/mol
Step 6: Calculate molar weight of M
Molecular weight of M = 129.6 - (2*35.45)
Molecular weight of M = 58.7 g/mol
M is cobalt (Co)
The element represented as M is Co.
Using the formula;
number of moles of hydrated salt = number of moles of anhydrous salt
We obtain;
Mass of hydrated salt/Molar mass of hydrated salt = Mass of anhydrous salt/Molar mass of anhydrous salt
Mass of hydrated salt = 2.9237 g
molar mass of hydrated salt = M + 179
Mass of anhydrous salt = 1.5941 g
Molar mass of anhydrous salt = M + 71
Substituting values;
2.9237/M + 179 = 1.5941/M + 71
2.9237(M + 71) = 1.5941(M + 179)
2.9237M + 207.5827 = 1.5941M + 285.3439
2.9237M - 1.5941M = 285.3439 - 207.5827
1.3296M = 77.7612
M = 77.7612/1.3296
M = 58.5
The element is Co
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