The bond is covalent in nature.
There is a sharing of electrons between these two atoms, giving rise to a covalent bond. The electronegativity value of H is 2.1 while that of O is 3.5 (Brown, LeMay and Bursten, 1991). There will hence be a distortion of the electron cloud, thus causing the molecule to be polar. The bonding between oxygen and hydrogen is polar covalent in nature.
Polar molecules are attracted to a charged rod. In these molecules, the centres of positive and negative charges do not cancel each other out, giving rise to permanent dipoles. When a positive rod is used, the negative end of the dipoles are attracted towards the rod while the positive end of the dipoles are attracted to a negative rod.
3. Using the 'electron pair repulsion theory', state and explain the shape of the following compounds and in each case sketcha diagram to show the arrangemant of the atoms in space, labelling the bond angles.
In AlCl3, the three outer electrons of the aluminium atom are bonded to the outer electrons of three chlorine atoms. Since there are no lone pair of electrons, the structure will not be distorted. According to the electron pair replusion theory, the three bonded pairs repel each other as far apart as possible. AlCl3 will hence be trigonal planar in shape with a bond angle of 120 (Brown, LeMay and Bursten, 1991).
In SiH4, the four outer electrons of the silicon atom are bonded to the outer electrons of four hydrogen atoms. There are no lone pair of electrons. According to the electron pair replusion theory, the four bonded pairs repel each other as far apart as possible. SiH4 will hence be tetrahedral in shape with a bond angle of 109.5.
In PCl5, the five outer electrons of the phosphorus atom are bonded to the outer electrons of five chlorine atoms. There are no lone pair of electrons. According to the electron pair replusion theory, the five bonded pairs repel each other as far apart as possible. The shape of PCl5 will be trigonal bipyramid, with bond angles of 120 and 90.
4. Enthalpy changes for the reactions of carbon and aluminium with oxygen are given in the following equations, where all substances are in their standard states.
C(s) + O2(g) CO2(g) H = -394 kJ mol -1
4Al(s) + 3O2(g) 2Al2O3(g) H = -3352 kJ mol -1
(a) What is the value for the standard enthalpy of combustion of carbon