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151. In Ostwald’s process for the manufacture of nitric acid, the first step involves the oxidation of ammonia gas by oxygen gas to give nitric oxide gas and steam. What is the maximum weight of nitric oxide that can be obtained starting only with 10.0 g of ammonia and 20.0 g of oxygen?

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152. Define electrochemical cell. What are the main requirements of an electro- chemical cell?

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Long Answer Type

153.
Discuss in brief the working of an electrochemical cell.

An electrochemical cell is also known as galvanic cell or voltaic cell. A redox reaction takes place in such cells. The oxidation and reduction take place in two separate beakers known as half cells. One beaker contains zinc plate dipped into a 0 .1M zinc sulphate solution. The second beaker contains copper plate dipped into a 0 . 1M copper sulphate solution. The two solutions are connected by an inverted U tube known as a salt bridge. The salt bridge is filled with a solution of an electrolyte such as KNO₃, KCl or NH₄NO₃(which does not undergo a chemical change during the process) to which gelatin or agar-agar has been added to make it semi-solid.

The ends of the salt-bridge are plugged with glass wool or cotton.

Reaction in a galvanic cell: When the two electrodes are connected through a copper wire, the reaction takes place and electric current begins to flow as shown by the ammeter. The following reactions occur at different electrodes:
At anode (Oxidation half-reaction):

At cathode (Reduction half reaction):

Oxidation takes place at anode and reduction takes place at the cathode. The electrons from the anode flow to the cathode. The anode is a negative electrode and cathode is a positive electrode. Zn²⁺ ions dissolve in the anode compartment while Cu²⁺ ions are deposited on the cathode. The neutrality of the two solutions is maintained by a salt bridge by providing cations and anions to replace the ions lost or produced in two half cells. The complete cell reaction is

In such cells, energy is liberated in the form of electrical energy.

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154. Explain the function of salt bridge in an electrochemical cell.

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Short Answer Type

155.

What are half cell reactions? Explain.

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156.

Write down the half reaction and net reaction for the Daniell cell.
$right enclose Zn left parenthesis straight s right parenthesis end enclose space Zn to the power of 2 plus end exponent left parenthesis aq right parenthesis vertical line vertical line space space Cu to the power of 2 plus end exponent left parenthesis aq right parenthesis space left parenthesis 1 space straight M right parenthesis space Cu left parenthesis straight s right parenthesis.$