Answer to Question #31130 in Chemistry for shreya

Question

1. electric decomposition is better than thermal decomposition. why?
2. what happens when aqueous solution of sodium sulphate reacts with aqueous barium chloride?
3.when a black metal compound XO is heated with colourless gas Y. X is a reddish brown colour which does not react with dilute acid a t all.

Answer 1

1.Thermal decomposition is the process of breaking down a chemical compound into simpler substance by heating it. The reaction is usually endothermic because heat is required to break the bonds present in the substance. Electrolysis is the process of forcing a chemical reaction that wouldn't normally occur on its own to happen by passing an electric current through the reactants. The key process of electrolysis is the interchange of atoms and ions by the removal or addition of electrons from the external circuit. The desired products of electrolysis are often in a different physical state from the electrolyte and can be removed by some physical processes. The amount of electrical energy that must be added equals the change in Gibbs free energy of the reaction plus the losses in the system. The losses can (in theory) be arbitrarily close to zero, so the maximum thermodynamic efficiency equals the enthalpy change divided by the free energy change of the reaction. In most cases, the electric input is larger than the enthalpy change of the reaction, so some energy is released in the form of heat.

2. Immediate milky appearance after 5-10 minutes a precipitate of BaSO₄ will settle out of solution the the solution will be clear. You will obtain a cloudy, white precipitate that will remain so infantily. This is a precipitation reaction (the formation of an insoluble salt from a solution of soluble ones) which occurs because barium sulfate is insoluble, so when mixed, the barium ions react with the sulfate ions to form a white precipitate of barium sulfate.

3. CuO - black metal compound; H₂ - colourless gas; Cu - reddish brown colour which does not react with dilute acid a t all
CuO + H₂ --> Cu + H₂O
(+2)(-2)..(0) -->(0)..(+1)(-2)

Oxidizing agent = a substance that gains electrons in a redox chemical reaction. The oxidizing agent is reduced.(gains electrons)
CuO + H₂ ==> Cu + H₂O