Question 1

Which of the following species cannot exist?

Accepted Answer

B^{3+} , being small in size, does not have empty d-orbitals like other atoms to accommodate 6 electron pairs of 6 F^{-}  ions.

Question 2

Question 3

When zeolite (hydrated sodium aluminium silicate) is treated with hard water, sodium ions are exchanged with:

Accepted Answer

Hint:  Zeolites act as water softeners that remove mineral ions from them. Correct Answer:  B Explanation :In the question, we are given hydrated sodium aluminium silicate, which is a zeolite. Now it is asked that when sodium aluminium silicate is heated with hard water then sodium ions are exchanged by which ion.The reaction between sodium aluminium silicate with hard water is as follows: Na_2O.Al_2O_3.nSiO_2.mH_2O+CaSO_4 \rightleftharpoons CaO. Al_2O_3.nSiO_2.mH_2O + Na_2SO_4 Here we can see that sodium ions are exchanged with  Ca^{2+}  ions. This removes the hardness of the water.Hence, during the reaction of zeolite i.e. sodium aluminium silicate with hard water the sodium ion of zeolite, will be exchanged with calcium and magnesium ions.So option  \mathbf{B}   i.e.  \mathrm{Ca}^{2+}  is correct.

Question 4

The monomer units of silicons, a water repellant, acid resistant and heat resistant polymer, is:

Accepted Answer

Alkyl group is water repellent and acid as well as heat resistant because of high bond energy. Hence, the monomer units of silicones as water repellant, acid-resistant and heat resistant polymer is  R_2Si(OH)_2 .Therefore, option C is correct.

Question 5

Oxalic acid is heated with concentrated  H_{2}SO_{4} . When the resultant gases are passed over red hot carbon,  X  is obtained. Here,  X  is:

Accepted Answer

When oxalic acid is heated with concentrated sulfuric acid, a mixture of  CO  and  CO_{2}  is obtained.  (COOH)_2 + H_2SO_4(l) \rightarrow H_2O + CO_2(g) + CO(g) + H_2SO_4(l)   H_{2}C_{2}O_{4}\xrightarrow[-H_{2}O]{H_{2}SO_{4}}CO+CO_{2} When this mixture is passed over red hot carbon,  CO_{2}  is reduced to  CO .  CO+CO_{2}\xrightarrow[\Delta ]{C}3CO The correct option is 'A'.

Question 6

Compound that combines with haemoglobin of blood to form carboxy haemoglobin is:

Accepted Answer

The highly toxic nature of CO arises due to the fact that it easily forms a complex with haemoglobin called carboxy-haemoglobin which is more stable than oxy-haemoglobin disrupting the oxygen supply in the body.

Some P-Block Elements