Chemistry Lab 111 Percent Water in a Hydrated Salt Pre Lah Questions Name: Partn

ID: 713501 • Letter: C

Question

Chemistry Lab 111 Percent Water in a Hydrated Salt Pre Lah Questions Name: Partner: Date: 1) Write the chemical formula for the following hydrated compounds; a) Iron (II) sulfate heptahydrate b) Sodium sulfide nonahydrate c) Lithium perchlorate trihydrate 2) Explain the difference between physical and chemical properties of the following chemicals a) CuSO4 (s) b) CuSO4 (aq) c) CuSO4.5 H20 (s) 3) The following data were collected from the gravimetric analysis of a hydrated salt: Mass of crucible and lid (g) Mass of crucible, lid, and hydrated salt (g) Mass of crucible, lid, and anhydrous salt (g) 37.466 42.342 40.244 Determine the percent water in the hydrated salt. (experimental data) CHEL 111 -Percent of Water in a Hydrated Salt Revised - Heidary&Allara; - 1

Explanation / Answer

Solution

(a) Iron (II) sulfate heptahydrate ---FeSO4.7H2O

(b) Sodium sulfide nonahydrate-------- Na2S.9H2O

(2)

Physical Properties

Chemical Properties

CuSO4 (s)

white or off-white solid, Melting point 200°C with decomposition

i) When heated to decomposition it emits toxic fumes of sulfur oxides

ii) decomposes to cupric oxide at 650°C

CuSO4 (aq)

Soluble in water

CuSO4 dissolves in water to form [Cu(H2O)6]2+

CuSO4 .5H2O

Blue crystalline powder. Melting point 110°C (with decomposition)

It decomposes at 150°C and converted into anhydrous salt, at 110°C, it converts into monohydrate.

Weight of hydrated salt = 42.342 – 37.466 = 4.876 g

Weight of anhydrous salt = 42.342 – 40.244 = 2.098 g

Amount of water = (4.876 - 2.098) g = 2.778 g

The percent of water in the hydrated salt = (2.778 g/4.876 g) x 100 = 56.97 % (answer)

The theoretical percent of water in CuSO4 .5H2O =

[(5 x 18 g/mol)/ 249.685 g/Mol] x 100

= 36.05%

The molar mass of hydrated sodium sulfate = 322.1 g/mol

The molar mass of anhydrated sodium sulfate = 142.04 g/mol

Amount of water = 322.1 - 142.04 = 180.06 g

No. of water molecule in hydrated sodium sulfate (x) = 180.06 g / 18 = 10

The formula of the hydrated sodium sulfate = Na2SO4.10H2O