139 Analysis of Alum NAME 144 Prentice Hall Laboratory Manual for Introductory C

Question

139 Analysis of Alum NAME 144 Prentice Hall Laboratory Manual for Introductory Chemistry 4. A hydrate of calcium sulfate, caso . r10. contains 20.9% water. Calculate the crystallization (X). and write the formula of the hydrate ater or 5. A hydrate of cobalt(II) chloride, CoCl ·XH0. decomposes to produce 46.1% water. Calculate the water of crystallization (), and write the formula of the hydrate 6. A hydrate of chronium(111) nitrate, Cr(NO),. XH.Q is foundto contain 60.2% anhydrous compound. Calculate the water of crystallization (X), and write the formula of the hydrate, 7. Coptional) Find the mass of water driven off when 1.252 g of strontium chiloride hexalydrate 7. ( SrCl, 6H,0, is decomposed by heating.

Explanation / Answer

4)

Let mass of hydrate be 100 g

mass of H2O = 20.9 % of mass of hydrate

= 20.9*100/100

= 20.9 g

Molar mass of H2O = 2*MM(H) + 1*MM(O)

= 2*1.008 + 1*16.0

= 18.016 g/mol

mass of H2O = 20.9 g

we have below equation to be used:

number of mol of H2O,

n = mass of H2O/molar mass of H2O

=(20.9 g)/(18.016 g/mol)

= 1.16 mol

Molar mass of CaSO4 = 1*MM(Ca) + 1*MM(S) + 4*MM(O)

= 1*40.08 + 1*32.07 + 4*16.0

= 136.15 g/mol

mass of CaSO4 = 79.1 g

we have below equation to be used:

number of mol of CaSO4,

n = mass of CaSO4/molar mass of CaSO4

=(79.1 g)/(136.15 g/mol)

= 0.581 mol

we have below equation to be used:

X = mol (H2O)/mol (CaSO4)

X = 1.16 / 0.581

X = 2

Answer:

x= 2

CaSO4.2H2O

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