Question

Give one example each of a chemical reaction characterized by
1.Evolution of a gas
2.Change in colour
3.Formation of a precipitate
4.Change in temperature
5.Change in state.

Answer 1

We are given here five types of the reactions. We need to write the example of the chemical reaction one by one. A chemical reaction is where two reactants react to form the product.

Complete step-by-step answer: Step1. Evolution of the gas:The evolution of gas means that when the product is formed the gas is released. You can know that either by the bubbles it forms or from the smell of it or the brisk effervesce it releases. The chemical reaction between dilute Sulphuric acid and zinc It form the zinc sulphate and hydrogen The reaction is $Zn(s) + {H_2}S{O_4}(aq) \to ZnS{O_4}(aq) + {H_2}(g)$
Step2. Change in color:The change in color is often used to find the functions in the compounds in the reaction. The reaction between the lead nitrate solution and potassium iodide. It changes the color of the reaction to yellow. The reaction is $Pb{(N{O_3})_2} + 2KI \to Pb{I_2} + 2KN{O_3}$
Step3. Formation of precipitate: Precipitate is a substance that is not soluble and it sticks at the bottom of the solution. One of the reactions is Barium chloride and sodium sulphate.The reaction is $BaC{l_2}(aq) + N{a_2}S{O_4}(aq) \to BaS{O_4}(s) + 2KNaCl(aq)$
Step4. Change in temperature.:There are times when the energy is released or absorbed. It makes the change in the temperature.
$Zn(s) + {H_2}S{O_4}(aq) \to ZnS{O_4}(s) + {H_2}(g)$\
Step5. Change in the state:The change in the state means that reactions are the physical state of the object like solid to liquid or the solid to the gas. One of the explanations is the burning of the wax. Wax turns into the liquid.

Note: When the camphor is burned to it changes directly into the gas. This process is called sublimation. When the energy is released it is an exothermic reaction.