Data Table 1 Analysis:
-None of the oxides formed acidic solutions with water. The oxides that did form alkaline solutions with water are Sodium Hydroxide (NaOH) and Magnesium Oxide (MgO). Aluminium oxide is the only oxide insoluble in water.
-Sodium hydroxide is a soluble oxide in which the sodium and hydroxide atoms separate into ions when it dissolves in the water.
NaOH ---- (H2O) ----> Na+ + OH-
Magnesium oxide is only slightly soluble in water mainly due to the metal’s greater charge density. The solution had a pH of 10 showing that it is slightly basic. This shows that there is a slight reaction that takes places with the water where hydroxide ions have been produced.
Equation of the reaction:
MgO(s) + H2O(l) → Mg(OH)2(aq) + H2(g)
- Aluminium is the only insoluble oxide that did not react with water. The oxide ions it contains are held too strongly in the solid lattice to react with water. However, it is amphoteric which means it reacts with both acids and alkalis.
Equation of the reaction:
with acids: Al2O3(s) + 6HCl(aq) ——> 2AlCl3(aq) + 3H2O(l)
with alkalis: Al2O3(s) + 2NaOH(aq) + 3H2O(l) ——> 2NaAl(OH)4(aq)
- Due to the 1st 3 oxides being only available, the trends drawn will be based on them only. Unfortunately with only 3 oxides, no trend in the states of oxides can be drawn from the results since the ones recorded all have the same state. The trend shown in the character of the oxides is that it begins with strongly basic oxides on the left hand side and changes to less basic and neutral oxides on the right hand side of the data table. The trend in the structures of oxides is from metallic ionic oxides on the left to less ionic substances on the right side.
Data Table 2 Analysis:
-Both NaCl and MgCl2 dissolve in water giving neutral solution that contains separate aqueous ions.
Sodium NaCl(s) ———> Na+(aq) + Cl¯(aq)
Magnesium MgCl2(s) ———> Mg2+(aq) + 2Cl¯(aq)
The reaction between water and aluminium chloride depends on the amount of water used. Since only a small amount of water is used, during the reaction there is a hissing sound and hydrogen chloride gas is given off as steamy acidic fumes.
AlCl3(s) + H2O(l) → AlCl2OH(s) + HCl(g)
Phosphorus (V) chloride has a violent reaction with water producing fumes of hydrogen chloride. As with the other covalent chlorides, if there is enough water present, these will dissolve to give a solution containing hydrochloric acid.
PCl5(s) + 4H2O(l) ———> H3PO4(aq) + 5HCl(aq)
As you go across the period the substances also start to react with water rather than dissolve it. The reactions with water also become more violent.
-Going from left to right, each element bonds to an extra chlorine in which it is noticed that the subscript of the Cl increases by one as you move across the period. The trend in the state of chlorides is that it changes from that of solids to liquids. The pH of solutions starts with a pH7 from the left hand side and starts to decrease as you go across the period. There is a change from neutral solutions on the left hand side to acidic solutions towards the right hand side. Another trend observed is that the structures changes from giant ionic lattices to simple molecular across the period
Conclusion and evaluation
The elements on the right hand side of period 3 such as sodium and Magnesium forms ionic bonds with oxygen and chlorine. All the elements after aluminium are non-metals and so form covalent bonds with oxygen and chlorine. There was a major limitation in the results due to the unavailability of all the oxides in the lab and so data analysis from data table 1 were based only on the 1st 3 oxides in the period. Therefore, trends could not be fully observed in the properties of the properties of oxides in period 3. The only major trend that can be found in the properties of the oxide is that goes from a strongly basic solution to a less and more neutral solution when it reaches aluminium oxide. However, the chlorides were all available and so solid results could be drawn from them. With the chlorides it starts with neutral solutions but across the period the pH decreases as acidic solutions are formed. The reactions of chlorides with water also became much more violent across the period..
The possible sources of error in this experiment may include:
- Material used may have been tampered with and so would affect the overall results.
- Wrong measurements were taken.
- Error arrising from human judgement.
Although my experiment was successful, many improvement could have been made to both my experiment and too the experiment. This includes:
- Repeating the measurements for more trials so that more accurate answers could be found.
- A possible modification to this experiment would be to use sodium oxide rather than sodium hydroxide.
- Make sure that none of the compound is accidentally spilled out.
