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.

In standard conditions, hydrogen and oxygen exist in a gaseous state, whereas water exists in a liquid state.

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

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.

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.

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 atomic number of F, O and N are Ǭ, 8 and Ǫ respectively and they belong to the same period i.e. 2nd period. The atomic radius decreases in moving from left to right along a period.

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.

Carboxylic acids are compounds which contain a group also known as carboxyl group.

Pencil lead is formed of graphite. Graphite is an allotropic form of carbon in which each carbon atom is joined to three others, forming layers

Cyclobutane is a cyclic hydrocarbon consisting of four carbon atoms where each carbon atom is attached to the two other carbon atoms and two hydrogen atoms.

As the compound, CH₃CH₂CH=CH₂ contains four carbon atoms and a double bond attached to the first carbon, so the I.U.P.A.C name of CH₃CH₂CH=CH₂ is But-1-ene.

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.

Magnesium metal never reacts with cold water but reacts with both hot water and steam to form magnesium hydroxide and hydrogen gas.

Due to the weaker bond of gallium atoms their melting point is also low.