Question

Experiment Properties of Solutions 112/ Roll No. Name: Section:__ Date: Post-lab Questions 1. Did you observe a difference in conductivity of deionized water and tap water. If yes, explain why there is a difference 2. What was the conductivity of solid sodium chloride? What was the conductivity of the mixture when water was added to the salt? Explain your observations 3. Indicate whether solutions of each of the following contain (a) only ions, (b) only molecules, or (c) mostly molecules and a few ions. Compound Type of particles in aqueous solution 1. Naci 2. NaOH 3. CHOH (Ethanol) 4. HCI 5. CH,COOH (Acetic acid) 6. NHU

Answer 1

Answer :

Q1.

Conductivity of Deionized water :

Deionized water is a water sample in which there is no dissolved ion present in it. All the dissolved ions present in it is removed by physical process to make deionized water.

Now, we know that conductivity of a solution is due to the presence of dissolved ion, becasue only the dissolved ion can carry the electron and hence electricity produced. In the absence of ion in water there will be no such agent to flow electron and no electricity is produced. But due to the very small dissociation of pure water some H⁺ and OH^- is produced which can flow electron with very very little extent as the amount of H⁺ and OH^- is very small and this conducance is almost negligible.

So, as in deionized water there is no dissolved ion, hence its conductivity is very small or negligible.

Conductivity of tap water :

In tap water there is different types of dissolved ions are present, such as Cl^-, Na⁺, K⁺​​​​​​, NH₄⁺ ect​​​​​​. Due to the presence of these dissolved ion the conductivity of tap water is very high compared to that of deionized water.

(ans)

Q2.

In solid sodium chloride (NaCl) the Na⁺ and the Cl^- ions are packed in a rigid crystal lattice. So these ions can't move from their position to conduct electron i.e. electricity. Thus solid sodium chloride does not conduct electricity and hence its conductivity is zero.

But when water is added to solid sodium chloride then NaCl dissolved in water and dissociation occurs. In aqueous solution, NaCl dissociates completely to form highly conducting Na⁺and Cl^- ion. In solution they are free to move and thus they can conduct electricity. So mixture of NaCl and water is a highly conducting solution.

(ans)

Q3.

NaCl = strong electrolytes ( i.e. NaCl completely dissociates in water to form its constituent ions i.e. Na⁺ and Cl^-). So in aqueous solution of NaCl contain only Na⁺ and Cl^- ion.

NaOH  $\rightarrow$  It is also a strong electrolyte. So aqueous solution of NaOH contains only Na⁺ and OH^-

C₂H₅OH $\rightarrow$  Ethanol does not ionise. So in aqueous solution of ethanol only molecular C₂H₅OH is present.

HCl $\rightarrow$ Hydrochloric acid (HCl) is a strong electrolyte. So in aqueous solution it is completely dissociated to H⁺ and Cl^- ion. So only H⁺ and Cl^- ions are present in aqueous solution of HCl.

CH₃COOH $\rightarrow$ It is acetic acid. It is a weak electrolyte. So it partially ionizes to H⁺ and CH₃COO^- ion. But its dissociation constant is very low. So its aqueous solution contains mostly molecular CH₃COOH and few H⁺ & CH₃COO^- ions.