Biochemistry Mid-Semester Exam — 2018 (Past Paper)

24 clinical MCQs in Biochemistry. The following are noble gases except;. Kenya, Africa and global revision.

Questions, Answers & Explanations

1. Q1. The following are noble gases except;

   • Hydrogen
   • Helium
   • Neon
   • Argon
   • Radon

   Answer: Hydrogen

2. Q2. The difference between Group IV and Group VI elements is that;

   • The latter are metals the former are non metals
   • The latter are non metals former are metals
   • The latter are very reactive while the former are relatively inert
   • The former are more reactive in comparison to the latter
   • All the above are incorrect

   Answer: The latter are metals the former are non metals

3. Q3. The following is true about d-orbitals;

   • accommodate a maximum of 14 electrons
   • have a minimum principal quantum number (n) of 2
   • an electron occupying the orbital can have a magnetic quantum number of -½
   • can have a principal quantum number (n) of 4
   • an electron in this orbital can have a magnetic quantum number of +½

   Answer: accommodate a maximum of 14 electrons

4. Q4. The strength of following acids is shown below. I II III IV V --- --- --- --- --- --- $K a=10^{-4}$ $K a=10^{-12}$ $K a=10^{-7}$ $pK a=12$ $pK a=6$ Which one is true?

   • I is the most acidic
   • II is the least acidic
   • III is less acidic than I
   • IV is more acidic than II
   • V is more acidic than IV

   Answer: I is the most acidic

5. Q5. In the molecule $CH 3CH 2CHCH 2$, the bond(s) between C4 and C5 from the left

   • is a sigma bond only
   • Has no pi bond
   • Consists of two pi and one sigma
   • Is pi only
   • Is none of the above

   Answer: is a sigma bond only

6. Q6. Magnetic quantum number

   • determines the shape of orbital
   • takes the value of $\pm ½$ only
   • is independent of angular momentum quantum number
   • determines the orbitals
   • none of the above

   Answer: determines the shape of orbital

7. Q7. The following is/are Lewis acid(s)?

   • $Co^2+$
   • $NH_3$
   • $CH_3$
   • $H_2O$
   • $O^2-$

   Answer: $Co^2+$

8. Q8. Ionic compound are due to;

   • Electron sharing between atoms
   • Electron transfer between atoms
   • The desire of an atom to gain electronic to rare gas elements
   • The fact that the resulting compound is lower in energy than either of the constituent ions
   • None of the above

   Answer: Electron sharing between atoms

9. Q9. In the Periodic Table, an element with high electron affinity

   • is likely to be in group 1
   • has high ionization energy
   • is likely to be in group I
   • can easily form ionic compound with group VI elements
   • Magnesium is a good example

   Answer: is likely to be in group 1

10. Q10. The following elements are paramagnetic, except;

    • N, 7
    • O, 8
    • F, 9
    • Cl, 17
    • He, 2

    Answer: N, 7

11. Q11. Dative bond

    • is possible between a molecule with complete octet and one with incomplete octet
    • involves sharing a pair of electrons as donated by the bonding atoms
    • involves complete transfer of a pair of electrons between bonding atoms
    • is not a covalent bond
    • All the above are false

    Answer: is possible between a molecule with complete octet and one with incomplete octet

12. Q12. The following are true on Molecular geometry except;

    • is dictated by the number of electron pairs on the central atom
    • 'bonding pair' electrons exerts the greatest repulsion
    • 'lone pairs' electrons exerts the greatest repulsion
    • is the arrangement in space of atoms bonded to a central atom
    • is dictated by the VSEPR-model

    Answer: is dictated by the number of electron pairs on the central atom

13. Q13. In the Periodic Table the atomic size of elements;

    • Increases across the Period
    • Increases down the Period
    • Decreases down the Period
    • Remains constant across the Group
    • None of the above is true

    Answer: Increases across the Period

14. Q14. In the molecule H - S - D the proton is;

    • easily lost when D is much more electronegative than S
    • easily lost when D is much less electropositive than S
    • Remains unchanged when D is replaced by a more electronegative element
    • easily lost when S and D are equal in electronegativity
    • None of the above is true

    Answer: easily lost when D is much more electronegative than S

15. Q15. With regards to the electronic structure of atoms the following rules applies; I. "No two electrons in an atom share all the four quantum numbers" II. "The most stable arrangement of electrons in orbital is the one with the greatest number of parallel spins"

    • I is Hund's rule
    • II is Pauli's exclusion principle
    • I is Pauli's exclusion principle while II is Hund's rule
    • I and II are never applicable at the same time
    • None of the above is true

    Answer: I is Hund's rule

16. Q16. An electron has the following properties?

    • Wave function
    • Magnetism
    • Mass
    • All the above
    • None of the above

    Answer: Wave function

17. Q17. In the periodic table;

    • Elements are arranged into s/s blocks
    • Transition elements are in the f-block
    • Electrons are added to s atomic orbital in p-block elements
    • All rare gas elements have $ns^2 np^6$ configuration
    • Electronegativity increases down the Group

    Answer: Elements are arranged into s/s blocks

18. Q18. The f orbital has

    • $l=3$
    • $n=3$
    • nine orbitals
    • sixteen orbitals
    • none of the above

    Answer: $l=3$

19. Q19. Expansion of octet

    • account for $SF_4$
    • account for $PCl_5$
    • does not involve hybridization of atomic orbital
    • accounts for the existence of Boron trifluoride ($BF_3$)
    • None of the above is true

    Answer: account for $SF_4$

20. Q20. Rank the following bonds in order of increasing bond strength

    • ionic, hydrogen bond, van der Waals, covalent single bond
    • van der Waals, hydrogen bond, ionic, covalent single bond
    • van der Waals, ionic, hydrogen bond, covalent single bond
    • covalent single bond, van der Waals, ionic, hydrogen bond
    • Ionic, covalent single bond, van-der Waals, hydrogen bond

    Answer: ionic, hydrogen bond, van der Waals, covalent single bond

21. Q21. The solubility of alcohols in water

    • Increases as the carbon chain length increases.
    • Decreases as the number of -OH groups present increases.
    • Increases with increasing molecular mass.
    • Is due to H- bonding between alcohol and water molecules
    • Increases there alcohol proof

    Answer: Increases as the carbon chain length increases.

22. Q22. In aldehydes, the carbonyl group is attached to

    • one hydrogen and one oxygen
    • one hydrogen and one alkyl group
    • two alkyl groups
    • one oxygen and one alkyl group
    • two hydrogen atoms

    Answer: one hydrogen and one oxygen

23. Q23. Hydrocarbons are not soluble in water because

    • The C-H bond is nonpolar.
    • They are lighter than water.
    • They are hydrophilic.
    • The C-H bond is polar.
    • They consist of hydrogen bonds

    Answer: The C-H bond is nonpolar.

24. Q24. The following statements are true regarding London forces, except

    • are present in all compounds
    • are stronger than hydrogen bonds
    • can occur between atoms or molecules
    • are due to electron movement and not to AEN
    • are naturally transient than dipole-dipole which are more permanent.

    Answer: are present in all compounds