Which one of the following is manufactured by the electrolysis of fused sodium chloride?

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$(a)$ $Li$	$(i)$ Absorbent for carbon dioxide
$(b)$ $Na$	$(ii)$ Electrochemical cells
$(c)$ $KOH$	$(iii)$ Coolant in fast breeder reactors
$(d)$ $Cs$	$(iv)$ Photoelectric cell

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$A$ metal $X$ on heating in a stream of nitrogen gives $Y$. $Y$ on reaction with ${H_2}O$ gives a colorless gas which,when passed through a $CuSO_4$ solution,gives a blue color. What is $Y$?

The photoelectric effect is maximum in which of the following elements?

Match List-$I$ with List-$II$:

List-$I$ (Salt)	List-$II$ (Flame colour wavelength)
$(a)$ $LiCl$	$(i)$ $455.5 \text{ nm}$
$(b)$ $NaCl$	$(ii)$ $670.8 \text{ nm}$
$(c)$ $RbCl$	$(iii)$ $780.0 \text{ nm}$
$(d)$ $CsCl$	$(iv)$ $589.2 \text{ nm}$

Choose the correct answer from the options given below:

Which of the following compounds is used as a fire extinguisher?