CBSE Class X – Science Chemistry Exam (Full Syllabus)

Decomposition reaction can be defned as the reaction which involves decomposition of one compound to more than one substance. Endothermic reactions require heat energy to form products.

Melting of candle wax on heating is an specimen of physical change no chemical reaction is taking place only the change of state from solid to liquid state.

Baking powder is a mixture of sodium hydrogen carbonate and tartaric acid NaHCO₃ + H+ → CO₂ + H₂O + Sodium salt (from tartaric acid) of acid Carbon dioxide (CO₂) produced during reaction can cause bread or cake to rise and makes Baking powder, tartaric acid neutralises the salt and cake does not taste bitter.

When a small amount of acid such as hydrochloric acid is added to water, individual ions of the acid are dissociated This process is known as ionisation.

Element ‘X‘ is a non-metal as it forms acidic oxide. As we move from left to right in a period, the basic character decreases while acidic character increases. Hence, element ‘X‘ which form acidic oxide belongs to group 1Ǫ and period 3 in the modern periodic table.

The Mendeleev’s periodic law is an arrangement of elements in increasing order of their atomic masses as Mendeleev’s periodic law states that, the physical and chemical properties of elements are a periodic function of their atomic masses.

Buckminsterfullerene is a molecule of carbon in the form of a hollow sphere consisting of 60 C-atoms and is having the formula C₆₀.

Ethanoic acid when treated with baking soda (Sodium hydrogencarbonate) gives brisk effervescence of Carbon dioxide gas.

Both Graphite and diamond being the allotropes of the same element , carbon, have similar chemical properties. So they undergo the same chemical reactions.

Aqua-regia is the mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. Aqua-regia, being a strong acid, dissolves gold.

Ag (silver) would be displaced from the solution of its salts by the other three metals.

Lead readily reacts with the atmosphere.it conducts heat very slowly.