Question

1. Copper (ll) oxide is a a. Black solid b. Brown gas c. Brown liquid d. White amorphous solid e. White crystalline solid 2. What is the valence (charge of the cation) of Cuo? a. 1 b. 2 c. 3 d. 4 3. 11.25 g of hydrated copper sulfate, CuSOıxHO, is heated until it lo mass is found to be 7.19 g. This 7.19 grams left are: a. A white or off-white powder b. Anhydrous c. Hygroscopic (will readily absorb water) d. all of the above 4. What is the gas generated in the equivalent weights experiment? a. Nitrogen b. Oxygen c. Hydrogen d. Chlorine e. None of the above 5. For FeCl, if you obtain an equivalent weight of 25 grams then what is the a weight in grams per mole? a. 25 b. 50

Answer 1

1. Copper(II) oxide is a black solid . It is present in the form of a mineral tenorite. Answer is a.

It can be prepared by heating copper in air around 300 – 800°C:

2 Cu + O₂ → 2 CuO

2. For ionic compounds the valency of any ion = charge of that ion.

Thus , the valency of Cu in cupric oxide, CuO is +2. Answer is b.

3. Hydrated copper sulphate i.e. CuSO₄.5H₂O molar mass = 249.6 g

loss of 5 H₂O (lattice water molecules) = 90

Anhydrous CuSO4 = 149.6

Loss Percentage = 90 / 249.6 X 100 = 36.05%

Given: Amount of CuSO4.xH2O = 11.25 g

Amount left = 7.19 g

Loss of mass = 11.25 - 7.19 = 4.06 g

Loss percentage = 4.09 / 11.25 x 100 = 36.35 %

Thus by co-relating with the above part one may understand that the remaining residue resembles an anhydrous , hygroscopic, white powder CuSO4. Thus the correct answer is d i.e. all of the above.

4. Equivalent weight  is the mass of one equivalent, that is the mass of a given substance which will combine with or displace a fixed amount of another substance. The gas generated during the equivalent weights experiment is hydrogen. Answer is c.