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Question 1

Q16. Which one of the following non-metals shows allotropy in the liquid state?

Carbon

Sulphur

Phosphorous

Bromine

Answer

Answer : Sulphur

Sulphur is a non-metal that shows allotropy in the liquid state. If sulphur is heated slowly the changes between the different forms can be observed. These changes are in the form of colour and viscosity (thickness) of the liquid. If the dark brown liquid sulphur is poured into a beaker of cold water, plastic sulphur is formed. This is an elastic, rubber-like form of sulphur. The tow commonly know allotropic forms of sulphur are monoclinic and rhombhic sulphur.
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Question 2

Q17. Which metal remains in liquid form at normal temperature?

Bromite

Mercury

Cadmium

Glass

Answer

Answer : Mercury

All metals except Mercury are solid at room temperature. Mercury is the only metallic element that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine. At room temperature and pressure, mercury neither readily share valence electrons with other atoms nor interact with each other to form a structure or lattice to become a solid.
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Question 3

Q18. In Modern Periodic Table, the atomic radius increases:

while moving from top to bottom in a group

while moving from right to left in a period

while moving from left to right in a period

None of the above

Answer

Answer : while moving from right to left in a period

The atomic radius is defined as the shortest distance between the atom’s nuclei and the outermost shell of the atom. The atomic radii of elements vary in the periodic table in a fixed pattern. In general, atomic radius decreases as we move from left to right in a period and it increases when we go down a group. This is because in periods the valence electrons are in the same outermost shell.
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Question 4

Q19. Which of the following is the chemical name of baking soda?

Sodium carbonate

Sulphate

Sodium hydrogen carbonate

calcium hydroxide

Answer

Answer : Sodium hydrogen carbonate

The IUPAC name baking soda (Sodium bicarbonate) is Sodium Hydrogen Carbonate. It is a chemical compound with the formula NaHCO₃. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion (HCO₃). It is primarily used in cooking (baking), as a leavening agent.
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Question 5

Q20. Chile saltpeter is the common name of:

Sodium nitrate

Potassium nitrite

Potassium nitrate

Sodium nitrite

Answer

Answer : Sodium nitrate

Sodium Nitrate (NaNO₃) is also known as Chile salt-peter or Peru saltpeter (due to the large deposits found in the Atacama desert in these countries) to distinguish it from ordinary saltpeter, potassium nitrate. Also known as soda niter, it is used in the production of fertilizers, pyrotechnics and smoke bombs, glass and pottery enamels, food preservatives, and solid rocket propellant
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