IB Docs (2) Team MC test: Covalent bonding
Multiple choice test on 4.2 Covalent bonding
Use the following 'quiz' to test your knowledge and understanding of this sub-topic. You will need access to a periodic table (Section 6 of the IB data booklet).
If you get an answer wrong, read through the explanation carefully to learn from your mistakes.
Which statements about covalent bonding are correct ?
I. Covalent bonds are formed by the electrostatic attraction between shared pairs of electrons and the positively charged nuclei on either side of the electrons.
II. Covalent bonds are directional.
III. Double bonds are always stronger than single bonds between the same two atoms.
Unlike ionic bonds, covalent bonds are directional. I is the definition of covalent bonds and you can check on III using Section 11 of the IB data booklet.
Which molecule contains the shortest distance between adjacent oxygen atoms in the molecule?
Hydrogen peroxide and tert-butyl hydroperoxide both contain an O−O single bond, ozone is a resonance hybrid with a bond order of 1.5 and oxygen contains an O=O bond which is the strongest and shortest.
Which substance will contain the strongest bond between the two carbon atoms?
Ethyne contains a carbon to carbon triple bond so is stronger than ethene and chlorethene which both contain a C=C double bond and ethane which contains a C−C single bond.
Which compound will contain the most polar bond?
Chlorine is more electronegative than bromine so the C−Cl bond in chloroethane is more polar than the C−Br bond in bromoethane. Carbon and hydrogen have very similar electronegativities so the bonds in ethane and ethene are almost non-polar.
Which statement explains why a covalent bond between two different atoms is polar?
Electronegativity specifically refers to the attaction towards the bonding pair of electrons with the more electronegative atom becoming δ− and the less electronegative atom becoming δ+. Electon affinity refers to the attraction towards a single electron in the gaseous state with non metals generally having more negative values than metals.
The structure of ethanoic acid is shown and the two carbon to oxygen bonds are labelled x and y.
Which is a correct statement about x and y?
The C=O double bond is both stronger and shorter than the C−O single bond as two pairs of electrons are being shared in the double bond.
The group 1 element sodium reacts with the group 17 element chlorine to form sodium chloride, which is ionic. The IB periodic table shows hydrogen as also being in group 1. Which factor correctly explains why the bonding in hydrogen chloride is covalent, not ionic?
The electronegativity of hydrogen is 2.2 whereas the value for sodium is 0.9. The value for chlorine is 3.2. The difference in values between hydrogen and chlorine is not enough for the electron from hydrogen to move completely to the chlorine atom to form a chloride ion so a pair of electrons is shared, although the bond is considerably polar.
Which contain polar bonds?
I. carbon dioxide, CO2
II. ammonia, NH3
III. methane, CH4
In each case there is a difference in electronegativity between all the bonding atoms. In methane this difference is small but the C−H bond will still be slightly polar. Do not confuse bond polarity with molecular polarity. Carbon dioxide and methane are non-polar molecules as the resultant dipole of all the polar bonds is zero due to their molecular shapes.
Which diagrams correctly show all the bond polarities?
.png)
The polarities in NF3 are reversed. Fluorine is more electronegative than nitrogen so the N should be 3δ+ and each F should be δ−.
Which compound contains both ionic and covalent bonding?
Calcium hydroxide contains Ca2+ and OH− so is ionic but the bond between the O and H in OH− is covalent. Lead(II) chloride, PbCl2 is ionic and both ethanol, C2H5OH and silicon tetrachloride, SiCl4 are covalent.
Twitter
Facebook
LinkedIn