CBSE Class X – Science Chemistry Exam (Full Syllabus)

Both these processes produce a cooling efect rather than heating. Dry ice absorbs heat from the environment to convert into gas. This feature makes it a good refrigerant. Processes of dilution of sulphuric acid and condensation of water vapours produce a large amount of heat. There fore these are exothermic processes.

When FeSO4 is heated strong, it decomposes to form a brown solid ferric oxide, sulphur dioxide and sulphur trioxide

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

The chemical reaction between dilute hydrochloric acid and granulated zinc is represented as follows:_x000D__x000D_Zn + 2HCl → ZnCl₂ + H₂↑

The tooth paste commonly used is alkaline or basic in nature as they contain mild bases such as sodium fuoride or sodium bicarbonate in their composition.

C₂H₅OH is not a base. C₂H₅OH is an organic compound with –OH functional group that is known as alcohol

On a pH scale acidity ranges from 1 to 7 and it increases by moving down from 7 to 1 while basicity ranges from 7 to 14 which increases by moving up from 7 to 14.

Atomic number X- 12 ,Y-17 Number of protons X-12, Y-17 Number of electrons X-12,Y- 17 Electronic configuration 2, 8, 2 2, 8, 7 Valence electrons X-2,Y- 7 Valency X- 2,Y- 1

The element with electronic confguration 2, 8 has octet confguration, so it must be an inert gas, i.e., neon, which is placed in group 18.

Carbon is an essential constituent of all organic compounds and it belongs to group 14.

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.

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.

A molecule of ammonia (NH₃) has only single bonds. The atomic number of N is 7. Its electronic configuration is ȷ2, Ǩȸ so it needs 3 more electrons to complete its octet.

Buckminsterfullerene is an allotrope of carbon with ǩ0 carbon atoms, which are arranged in the shape of a football. Since this also looks like the geodesic dome designed by the US architect Buckminster Fuller

Reaction between an acid and an alcohol results in the formation of ester, and the reaction is named as esterification.

Na (sodium) and Ca (calcium) react vigorously with water. Mg (magnesium) respond with water less vigorously than calcium and sodium. Fe (iron), on the other hand, does not react with cold as well as hot water instantly.

Because it is a covalent compound formed by sharing of electrons. Whereas in other three compounds are ionic compounds and they conduct electricity in their molten state.

PVC is a polymer and a bad conductor of electricity. It is the most common insulating material used to insulate electrical conductors from electric charge, thus preventing direct human contact with electricity.

Test tube C contains chemical mixture called aqua-regia. It is a mixture of concentrated HCl and concentrated HNO3  in the ratio of 3:1. Aqua-regia dissolves gold (Au) and platinum (Pt) in it, while hydrochloric acid and nitric acid do not.