Calculate the theoretical % H_2O in the hydrate M_gSO_4.-7H_2O Molar mass of M_g

Question

Calculate the theoretical % H_2O in the hydrate M_gSO_4.-7H_2O Molar mass of M_gSO_4.-7H_2O: 246.4 gram/mole Molar mass of H_2O: 18 grams/mole When a 2.000 g sample of CuSO_4 '5H_2O(s) was heated to dryness, the mass of the anhydrous salt remaining was found to be 1.30 g. What is the experimental value of the percent water of hydration? KCIO_2 thermally decomposes to generate O_2 gas the reaction Is; 2KCIO_3 (s) rightarrow 2KCI (s) + 3O_2 (g) If 0.32 grams O_2 are generated, how many grams KCIO_3 have been decomposed? Calculate the number of moles O_2, generated. From that, calculate how. many moles KCIO_3 have decomposed.] Molar mass KCIO_3 = 122g/mole molar mass O_2 = 32g/mole

Explanation / Answer

Q1.

theoretical % H2O in MgSO4*7H2O

total MW = MgSO4 + 7*H2O =246.4 + 7*18 = 372.4 g/mol

mass of H2O = 7*18 = 126 g of H2O

so % H2O = 126/(372.4)*100 = 33.83 %

Q2

m = 2 g of CuSO4*5H2O

mass of salt = 1.30 g of CuSO4

then

% water

total mass = 2

mass of water = 2-1.30 = 0.7 g

so

% mass of water = 0.7/2 * 100 = 35%

Q3

2KClO3 = 2KCl + 3O2

m = 0.32 g of O2

find KClO3

mol of O2 = mass/MW = 0.32/32 = 0.01 mol of O2

so ratio is 2:3

2/3*0.01 = 0.006666 mol of KClO3

mass = mol*Mw = 122*0.006666 = 0.81325 g of KClO3

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