CBSE Class X – Science Chemistry Exam (Full Syllabus)

Potassium iodide on reacting with lead nitrate gives yellow precipitate of lead iodide.KI + Pb(NO3)2 → PbI2 + KNO3

Chemical reaction in beakers A and B gives out heat. Hence, the temperature of the solution increases. Thus, we can call it an exothermic reaction._x000D_In beaker C, heat is absorbed from water instead and hence, the temperature decreases. Thus, we can call it an endothermic process.

Combination reactions form a new product with the combination of more than one reactant molecules.

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.

hydrogen-containing compound such as glucose is not categorized as acid because it does not produce hydrogen ions or some other ions, when dissolved in water, and consequently does not conduct electricity

Acids turn blue litmus solution to red. They have a sour taste as in the case of vinegar and are sticky to touch. On the other hand, bases turn red litmus solution to blue. Bases are bitter in taste as in the case of baking soda and are slippery to touch.

The elements boron (B), silicon (Si) and germanium (Ge) exhibit intermediate properties of metals and non-metals, therefore, they are called as metalloids

Atomic number 14 (electronic confguration of 2,8,4) is for silicon element, which is a metalloid and exhibit properties of both metal and non-metal

Eka-aluminum (later identified as gallium) has a valency of 3. Hence, the oxide would be of the molecular formula E₂O₃. Other options have a different valency of E.

As we move down in a group, the metallic nature of elements increases.  Be, Mg and Ca are present in the same group (group 2 of the modern periodic table).

Denatured alcohol is the ethyl alcohol which has been made unfit for drinking purpose by adding small amount of poisonous substance like methanol, pyridine, etc.

Prolong heating of red hot iron with steam forms Fe₃O₄ with hydrogen gas.

Aluminum is more reactive than iron, it displaces iron from ferrous sulphate solution. The green colour of ferrous sulphate solution slowly changes to brown as iron is formed.

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