31.

Thermite is a mixture of X parts of ferric oxide and Y parts of aluminium powder. X, Y respectively are

• 3, 1

• 3, 2

• 1, 1

• 2, 3

Which of the following is used for making optical instruments ?

• SiO₂

• Si

• SiH₄

• SiC

Which of the following statements is not correct?

• In oxyhaemoglobin Fe²⁺ is paramagnetic.

• During respiration the size of Fe²⁺ increases when it changes from diamagnetic to paramagnetic state.

• Four heme groups are present in haemoglobin

• Heme is the prosthetic group and it is non-protein part.

Which of the following is not correct ?

• SiO₂ is used as acid flux

• The distance between the layers in graphite is 3.35 × 10^-3 cm.

• SiO₂ reacts with Na₂CO₃ and liberates CO.

• The hybridisaton of C in graphite is sp².

Identify B in the following reaction

H₄SiO₄ $\underset{-{\mathrm{H}}_2\mathrm{O}}{\overset{1000°\mathrm{C}}{\to }}$ A $\underset{∆}{\overset{\mathrm{Carbon}}{\to }}$ B + CO

• corundum

• quartz

• silica

• carborundum

The chemical formula of feldspar is

• KAlSi₃O₈

• Na₃AlF₆

• NaAlO₂

• K₂SO₄.Al₂(SO₄)₃4Al(OH)₄

An oxide of an element is a gas and dissolves in water to give an acidic solution. The element belongs to

• II group

• IV group

• VIII group

• Zero group

Diborane reacts with ammonia under different conditions to give a variety of products. Which one among the following is not formed in these reactions?

• B₂H₆ 2NH₃

• B₁₂H₁₂

• B₃N₃H₆

• (BN)_n

SiCl₄ on hydrolysis forms 'X' and HCl. Compound 'X' loses water at 1000°C and gives 'Y'. Compounds 'X' and 'Y' respectively are

• H₂SiCl₆, SiO₂

• H₄SiO₄, Si

• SiO₂, Si

• H₄SiO₄, SiO₂

Which one of the following statements is not correct?

• Moissan boron is amorphous

• The reaction between boron and concentrated HNO₃, gives N₂O.

• Amorphous boron on heating with oxygen forms B₂O₃.

• Boron is a non-conductor of electricity.