Determination of conductance of various solutions - Assignment Example

Determination of conductance of various solutions Determination of conductance of various solutions Post laboratory questions This experiment was about determining the relationship between conductance and different concentrations of the same solution. It also involved determination of conductance values for various solutions and comparing them to determine which strong electrolytes, weak electrolytes or non-electrolytes are. From the data obtained it was clear to categorize all the solutions in the experiment according to their conductance values.

The solutions whose ions dissociate fully in aqueous solution produced the highest conductance while those that dissociated partially gave lower conductance and hence were classified as strong and weak electrolytes respectively. The conductance of hydrochloric acid was found to increase with increase in concentration. This can be attributed to increase in the number of ions in the aqueous solution responsible for conducting electric current. 2. Below is a graph showing the relationship between the conductance of HCl and its concentration.

The graph shows a linear relationship between concentration and conductance implying that an increase in concentration leads to a proportional increase in conductance. 3. Out of all the solutions analyzed the strong electrolytes are: HCl, HNO3, KOH, KNO3, Ca (NO3)2, Al (NO3)2, CuSO4, KCl. The weak electrolytes are: CH3CO2H, H2Oand NH3 The non-electrolytes are: ethanol. 4. From the data collected in the experiment the following have been classified as either strong acid, weak acid, strong base or weak base.

HCL- strong acid HNO3- strong acid KOH- strong base CH3CO2H- weak acid NH3- weak base 5. KNO3, Ca (NO3)2, Al (NO3)2, HNO3. All these compounds have the same anion i.e. NO3- but differ only in the cation present. This difference brings about the difference in their conductance. The differences arise due to difference in mobility of the various cations. All those metals plus hydrogen have different mobility in aqueous form therefore will conduct electric current differently. 6. The conductance of KCl is 660µS while that of KNO3 is 2.9mS. These two values differ due to the conductance contributed by nitrate and chloride ions to the total conductance of the solution.

Therefore based on the same principle NaNO3 is expected to have a higher conductance than NaCl. 7. From the conductance of KCl, HCl, and HNO3 the conductance of KNO3 can be calculated as: LKNO3 = LKCl+ LHNO3 - LHCl LKNO3 = 0.66mS+8.6mS-8.1mS LKNO3 = 1.16mS. This predicted value is far much lower than the experimental value measured. 8. a) The conductance value for tap water was 0.2mS signifying that it was a weak electrolyte. Therefore it did not contain any ionic impurities since they would have given a higher conductance value. b) The tap water could have contained molecular impurities which were responsible for the small conductance recorded.

These impurities partially dissolved in the aqueous solution and hence recorded the small conductance value observed.