Periodic elements CHM 331

1.     Which of the following is the most abundant metal in the earth’s crust?

• a. Aluminium

• b. Sulphur.

• c. Oxygen

• d. Gallium

2.     Bauxite contains one or more of the following

• a. Al2O3 

• b. Al2O3 and iron oxide

• c. Al2O3 and iron nitrate 

• d. Al3O2 

3.     Amongst the group elements, gallium has the lowest melting point because

•   a. Its lower in the group 

• b. its size is very small

• c. it consists of gallium molecules

• d. it’s a gas

4.     Why does boron not exist as B³⁺ in its compounds?

• A.    presence of d-orbital 

• b. low screening effect

• c. sum of the first three ionisation enthalpies for Boron is very high

• d. inert pair effect

5.     Small-scale preparations of Carbon monoxide involves

• a.      hydration of methanoic acid with conc. H₂SO₄   

• b. dehydration of methanoic acid with conc. H₂SO₄

• c. dehydration of methanoic acid with H₂SO₄

•  d. hydration of dilute HCl

6.     Why is CO bond the strongest known in a stable molecule?

• a.      The ground state of CO is a singlet state with a double bond comprised of one covalent bonds and one dative covalent bond

• b.     The ground state of CO is a singlet state with a triple bond comprised of two covalent bonds and one dative covalent bond

• c.      The ground state of CO is a singlet state with a triple bond comprised of one covalent bonds and two dative covalent bond

• d.     The ground state of CO is a triplet state with a triple bond comprised of one covalent bonds and two dative covalent bond

7.     Why is CO toxic to heamoblobin?

• a.      Instability of CO  

• b. ability to dissociates in solution

• c. ability to form stable complex 

• d. ability to form free ions in solutions

8.     Which of the following is used to provide inert atmospheres?

• a.      Liquid nitrogen

• b. solid nitrogen 

• c. Gaseous nitrogen

• d. free nitrogen

9.     Which of the following metals is toxic and present in ground water

• a. Antimony

• b. Arsenic 

• c. Bismuth

• d. Gallium

10. The following are oxides of nitrogen except

• a. Bi₂O₃

• b. N₂O₃

• c. P₄O₈

• d. Sb₄ O₈