Question

Colourless solution of silver nitrate is taken in two test tubes A and B. Metal plates of copper and platinum are dipped into test tubes, A and B, respectively. Content of test tubes,
A. B turns green
B. B turns blue
C. A turns blue
D. A remains colourless

Answer 1

Hint: Metals can be arranged based on their order of reactivity, called the reactivity series. The more reactive metals are arranged on top of the series. The more reactive metals can displace less reactive metal from their salt solution.

Complete step by step answer:
The reactivity series of metals, called the activity series, refers to the arrangement of metals in the decreasing order of their reactivity. Metals are substances that readily lose electrons and form cations. They also react with atmospheric oxygen to form metal oxides. But different metals have different reactivity towards oxygen. All these properties are explained by the reactivity series of metals.
The decreasing order of reactivity of some metals are,
Potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, hydrogen, copper, silver, gold.
Some of its features are,
A. The metals at the top of the reactivity series are strong reducing agents as they can be easily oxidized. These metals corrode very easily.
B. The reducing ability of the metals decreases down the series.
C. The electropositivity of the elements decreases down the reactivity series of metals.
D. All metals above hydrogen in the activity series can liberate hydrogen gas on reacting with acids.
Metals that are present higher on the reactivity series can displace metals that are placed lower from their salt solutions. In the above question, gold is the only element present below silver, as it is less reactive than silver. So, it cannot displace silver from its salt​solution.
In test tube A, copper is more reactive than silver so displacement reaction takes place, it displaces silver from silver nitrate solution forming blue coloured copper nitrate solution. The chemical reaction is written as:
\[{\text{Cu + Ag}}{\left( {{\text{N}}{{\text{O}}_{\text{3}}}} \right)_{\text{2}}} \to {\text{Cu}}{\left( {{\text{N}}{{\text{O}}_{\text{3}}}} \right)_{\text{2}}}{\text{ + Ag}}\]

Hence, the answer to the given question is option C. A turns blue .

Note: Non-metal has a relatively low boiling point, and most non-metals are gases and non-metals are poor heat conductors, and solid non-metals are dull and brittle. Some of them are strongly reactive, while others are in no way reactive.
Metals can react with water to form the corresponding hydroxide, liberating hydrogen gas. They react with acids to form metal salt with the liberation of hydrogen gas. They are good conductors of heat and electricity.