A sample of the hydrate of sodium carbonate has a mass of 8.85 g. It loses 1.28

Question

A sample of the hydrate of sodium carbonate has a mass of 8.85 g. It loses 1.28 g when heated. Find the formula and the name of the hydrate. A 16.4 g sample of hydrated calcium sulfate is heated until all the water is driven off. The calcium sulfate that remains has a mass of 13.0 g. Find the formula and the chemical name of the hydrate. When 8.00 g of Pb(C_2H_3O_2)_2 middot xH_2O are heated, 1.14 g of H_2O are driven off. Find the chemical formula and the name of the hydrate. A hydrate is determined to be 45.43% water and 54.57% COCI_2. Find the chemical formula and name for this hydrate.

Explanation / Answer

Question # 4

A sample of the hydrate of sodium carbonate has a mass of 8.85 g. It loses 1.28 g when heated.Find the formula and the name of the hydrate

Answer:

Mass of hydrated sodium carbonate is 8.85 g

Mass of water present in hydrated sodium carbonate is 1.28 g

Mass of anhydrous sodium carbonate is =8.85 g-1.28 g= 7.57g

7.57g of anhydrous sodium carbonate has 1.28 g of water.

Molar mass of anhydrous sodium carbonate = 105.9888 g/mol

105.9888 g of anhydrous sodium carbonate has = [(1.28 gx 105.9888g)/7.57g ]of water

                                                       =17.92 g of water = round of to18.0g of water

105.9888 g of anhydrous sodium carbonate has 18.0g of water(molar mass of water is 18g/mol)

1mole of anhydrous sodium carbonate has 1mole of water.

Answer: The name of the hydrate is sodium carbonate monohydrate =Na2CO3.H2O

Question # 5

A 16.4 g sample of hydrated calcium sulfate is heated until all the water is driven off. The calcium sulfate that remains has a mass of 13.0 g. Find the formula and the chemical name of the hydrate

Answer:

Mass of hydrated calcium sulfate is 16.4 g

Mass of anhydrous calcium sulfate is 13.0 g

Mass of water present in hydrated calcium sulfate = (16.4 g - 13.0 g)= 3.4 g

13.0 g of anhydrous calcium sulfate has 3.4 g of water

Molar mass of anhydrous calcium sulfate = 136.14 g/mol

136.14 g of anhydrous calcium sulfate has [(3.4 g x 136.14 g/mol)/13.0g ]of water

=35.60 g of water = round of to 36.0g of water

136.14 g of anhydrous calcium sulfate has 36.0g of water(molar mass of water is 18g/mol)

1mole of anhydrous calcium sulfate has 2 moles of water

Answer: The chemical name of the hydrate calcium sulphate dehydrate=CaSO4.2H2O

Question # 6

When 8.00 g of Pb(C2H3O2)2 · xH2O are heated, 1.14 g of H2O are driven off. Find the chemical formula and the name of the hydrate.

Answer:

Mass of Pb(C2H3O2)2 · xH2O is 8.0 g

Mass of water present in Pb(C2H3O2)2 · xH2O is 1.14g

Mass of Pb(C2H3O2)2 = (8.0 g -1.14g)= 6.86g

6.86g of Pb(C2H3O2)2 has 3.4 g of 1.14g of water

Molar mass of anhydrous Plumbous acetate [Pb(C2H3O2)]= 325.29 g/mol

325.29 g of anhydrous Plumbous acetate has [(1.14g x 325.29 g /mol)/ 6.86g]of water

                                                             =54.05g of water= round of to 54.0g of water

325.29 g of anhydrous Plumbous acetate has 54.0g of water

1mole anhydrous Plumbous acetate has 3 moles of water(molar mass of water is 18g/mol)

Answer: The chemical formula of the hydrate Pb(C2H3O2)2 · 3H2O and the name of the hydrate is Plumbous acetate trihydrate

Question #7

A hydrate is determined to be 45.43% water and 54.57% CoCl2. Find the chemical formula and name for this hydrate. (*Hint – assume that there is 100 g total of hydrate compound.)

Answer:

54.57% CoCl2 has 45.43% water

100 % CoCl2 has 83.25% water

Molar mass of CoCl2 is 129.839 g/mol

129.839 g/mol of CoCl2 has 83.25% water= 108.09g of water= round of to 108.0g of water

                                                                  = 108.0g/18= 6 moles of water

Answer: the chemical formula of this hydrate CoCl2.6H2O and name for this hydrate Cobaltous chloride hexahydrate

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