CBSE Class X – Science Chemistry Exam (Full Syllabus)

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.

In Combination and Exothermic reaction, Calcium oxide (CaO), reacts vigorously with water to produce calcium hydroxide (slaked lime) and produces a large amount of heat. Since calcium oxide and water combine to form a single product, calcium hydroxide. So this is a combination reaction.

This reaction is a double displacement reaction as well as a precipitation reaction. This is a double displacement reaction because one component of each compound has exchanged places with each other

The increasing order of acid strength is water < acetic acid < hydrochloride acid. Hydrochloride acid is a strong acid and ionises fully in water.

Phenolphthalein solution is a colourless indicator which gives pink colour in basic solution. Phenolphthalein solution remains colourless in acidic solution as well as in neutral solution.

Baking soda’s formula does not show any relationship water molecules.

washing the hands with water will dilute the acid and wash it out. Any remaining acid will be neutralized with sodium hydrogen carbonate (baking soda) as it is a base. This will minimize the effect of damage caused by acid to the skin.

Sodium carbonate (Na₂CO₃) is the salt of carbonic acid (H₂CO₂) and sodium hydroxide (NaOH). Here NaOH is a powerful base and carbonic acid is a weak acid.

Elements having the same number of valence electrons belong to the Same group.

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.

The elements of the 2nd period contain two shells: K and L shell. So, the outermost shell is L.

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

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

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.

A cation is formed by loss electrons from the atom of an element which acquires positive charge due to the presence of greater number of protons as compared to that of electrons.

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

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.