Name Date Section Conductivity of Solutions Postlab Questions 1. Dilute solution

Question

Name Date Section Conductivity of Solutions Postlab Questions 1. Dilute solutions of sulfuric acid (H2SO.) and barium hydroxide (Ba(OH)2) are each good conductors of electricity. However, as one solution is poured into the other, the light bulb of the conductivity apparatus dims. Explain this observation using the balanced chemical equation 2. Ordinary soda is a decent conductor of electricity. Listed below are some of the ingredients. Circle two ingredients that are responsible for the conductivity. Explain your answer a. Carbonated water (water with CO2) b. High fructose corn syrup (a sugar) c. Phosphoric acid (HyPO4) d. Sodium benzoate (NaC,H 02) e. Caffeine (molecular organic compound) Predict which of the following solutions would have a greater conductivity: 0.5 M NaCI or 0.5 M FeCls. Explain your reasoning. 3. Solutions of NaCI and AgNO3 are mixed. The light bulb remains bright even though a solid is formed. Explain this observation using the balanced chemical equation. 4. Revised 1/17/17

Explanation / Answer

1. Electricity is conducted can by ions in a solution.

Hence, dilute solutions of H2SO4 (H+ and SO4 2-) and BaOH2 ( Ba 2+ and OH-) will conduct electricity owing to the ions in solution.

However, if we mix the two solutions, following reaction occurs:

H2SO4 + BaOH2 --> BaSO4(ppt) + 2 H2O

Here, BaSO4 is insoluble in solution( will precipitate out) and H2O had weak ionization.

Hence, there will be far less ions to conduct electricity in solution.

And the light bulb will dim out as a result.

2. We will choose chemicals which ionize in water and hence will help in conduction of electricity.

We can choose carbonated water and phosphoric acid.

Carbonated water ( H2O + CO2 --> H2CO3 carbonic acid)

which ionizes partially as H2CO3--> 2H+ + CO3 2-.

and phosphoric acid H3PO4 which ionizes as

H3PO4 --> 3H+ + PO4 3-

These acids give multiple ions in solution but are weak acids ( hence weak ionization), therefore soda is only a decent conductor of electricity.

3. 0.5 M NaCl or 0.5 M FeCl3

same molarity means same number of molecules in solution. But on ionization, FeCl3 will give more ions than NaCl as shown below:

FeCl3 --> Fe 3+ + 3 Cl -  4 ions

NaCl --> Na+ + Cl- 2 ions

Hence, FeCl3 will conduct more charge and is a better conductor.

4. In this case, AgNO3 + NaCl ---> AgCl (ppt)+ NaNO3

Here, like in part 1, AgCl will precipitate out and have no role in conduction. But, NaNO3 is still present in solution which ionizes strongly and hence the light bulb will remain bright due to good conduction in solution.

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