Class 10 Science 2023 Board Exam

Which of the following is an example of endothermic process ?

In order to balance the following chemical equation, the values of the coefficients $x$ and $y$ respectively are :
$\mathrm{x}\mathrm{Pb}(\mathrm{N}{\mathrm{O}}_3{)}_2\stackrel{\text{Heat}}{\to }2\mathrm{PbO}+\mathrm{y}\mathrm{N}{\mathrm{O}}_2+{\mathrm{O}}_2$

What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together ? Name the type of reaction and write the chemical equation for the reaction that occurs.

When copper powder is heated in a watch glass, a black substance is formed.
(i) Why is this black substance formed ? Name it.
(ii) How can this black substance be reversed to its original form ?

Silver chloride kept in a china dish turns grey in sunlight.
(a) Write the colour of silver chloride when it was kept in the china dish.
(b) Name the type of chemical reaction taking place and write the chemical equation for the reaction.
(c) State one use of the reaction. Name one more chemical which can be used for the same purpose.

During electrolysis of water, if the volumes of oxygen and hydrogen evolved at the electrodes are $V_O$ and $V_H$ respectively, then $\frac{V_O}{V_H}$ is

Write down the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Nitrogen gas is treated with hydrogen gas to form ammonia gas.
(b) Lead nitrate is heated strongly to form lead monoxide, nitrogen dioxide and oxygen.
(c) A copper wire is dipped in silver nitrate solution and a shining deposit of silver is produced.

(a) Define oxidation.
(b) Identify the oxidising agent in the following reactions and balance the chemical equations :
(i) $\mathrm{P}{\mathrm{b}}_3{\mathrm{O}}_4+\mathrm{HCl}⟶\mathrm{PbC}{\mathrm{l}}_2+\mathrm{C}{\mathrm{l}}_2+{\mathrm{H}}_2\mathrm{O}$
(ii) $\mathrm{Mn}{\mathrm{O}}_2+\mathrm{Al}⟶\mathrm{Mn}+\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$

$\mathrm{Mn}{\mathrm{O}}_2+\mathrm{x}\mathrm{HCl}⟶\mathrm{MnC}{\mathrm{l}}_2+\mathrm{y}{\mathrm{H}}_2\mathrm{O}+\mathrm{z}\mathrm{C}{\mathrm{l}}_2$
In order to balance the above chemical equation, the values of $x$, $y$ and $z$ respectively are :

The emission of brown fumes in the given experimental set-up is due to