(a)(i) List three properties of elements which increase generally across a period in the Periodic Table,
(ii) Give two differences between a chemical reaction and a nuclear reaction.
(b) Use the information provided in the table below to answer Questions (i) – (vii).
|
Atom of Element |
P | Q | R | S | T |
|
Mass Number |
16 | 40 | 35 | 18 | 20 |
|
Atomic Number |
8 | 20 | 17 | 8 | 10 |
Which of the atoms in the table above:
(i) are isotopes of the same element?;
(ii) contains 18 neutrons?;
(iii) is chemically unreactive?;
(iv) readily forms an ion with two positive charges?
(v) attain an octet structure by accepting one electron?;
(vi) forms ionic bond with R?;
(vii) belongs to the s-block in the Periodic Table?
(c) Describe in outline how each of the following conversions can be carried out in the laboratory. Write appropriate equations for the reactions involved in each case
(i) CuCO\(_3\) to Cu
(ii) MgO to MgSO\(_4\).
Explanation
(a)(i) Electronegatively, ionisation energy, electron affinity.
(ii)
|
Chemical reaction |
Nuclear reaction |
|
- Involves only the electron |
- Involves the nucleus |
|
- Not usually accompanied by great heat change |
- Usually accompanied by a lot of heat change |
|
- New elements are not formed |
- New elements are formed |
|
- External factors such as pressure, temperature and catalyst affect the rate of reaction. |
- Not affected by external factors |
(b)
|
Atom of elements |
P | Q | R | S | T |
|
Mass number |
16 | 40 | 35 | 18 | 20 |
|
Atom number |
8 | 20 | 17 | 8 | 10 |
(I) P and S are isotopes of the same elements
(ii) R contains 18 neutrons
(iii) T is chemically unreactive
(iv) Q readily forms an ion with two positive charges
(v) R attains an octet structure by accepting one electron
(vi) Q forms an ionic bond with R
(vii) Q belongs to the s - block in the periodic table
(c)(i) To convert CuCO\(_3\) to Cu, heat strongly ; CuCO\(_3\) -> CuO + CO\(_2\) . Pass hydrogen over heated residue of CuO. H\(_2\) + CuO ---> Cu + H\(_2\)O
or pass NH\(_3\) over heated copper II oxide. 2CuO + 3NH\(_3\) —› 3Cu + 3H\(_2\)O + N\(_2\)
OR add dilute mineral acid to CuCO\(_3\) to form soluble salt: CuCO\(_3\) + 2HCI -> CuCl\(_2\) + H\(_2\) O + CO\(_2\) . Electrolysis using platinum electrodes or any inert electrode. Equation at the cathode Cu\(^{2+}\) + 2e\(^-\) \(\to\) Cu
OR add mineral acid to CuCO\(_3\) to form soluble salt CuCO + 2HCI -> CuCl\(_2\) + H\(_2\)O+ CO\(_2\) then add reactive metal e.g. Zinc or Aluminium CuCl\(_2\) + Zn -> Cu + ZnCl\(_2\)
(ii) To convert MgO to Mg\(_2\)SO\(_4\) , acid dilute H\(_2\)SO\(_4\) to excess MgO, filter off excess MgO. The filtrate is MgSO\(_4\) , MgO + H\(_2\)SO\(_4\) -> MgSO\(_4\) + H\(_2\)O. Evaporate / heat to dryness to obtain MgSO\(_4\).