Le Chatelier\'s Principle Equilibrium Lab link to lab instructions: https://web.

Question

Le Chatelier's Principle Equilibrium Lab

link to lab instructions: https://web.coas.missouri.edu/~chemweb/chem1330/docs/chem_eq_new.pdf

Not sure how to answer the questions in this lab. In particular:

PART 1: Ca(+2)(aq) + 2OH-(aq) ---> Ca(OH)2(s)

observations:

3. HCl added to test tube with Ca(OH)2 and the solid Ca(OH)2 precipitate dissipated and the pink color changed back to white.

What happens to the OH- ions?

Which OH- ions are reacting? the ones in the precipitate or in solution or both? How do you know?

What happens at the moleulcar/ionic level as the HCl is added?

What's the role of H+? Cl-?

List all species present at the end.

PART 2: CH3CO2H + OH- --> CH3C2- + H2O

observations we saw:

1. when added methyl orange to test tube of acetic acid it turned transparent light redish pink

2. when added NaOH to it, it changed to transparent orange

3. when added HCl it turned transparent light redish pink color again

What happens at the molecular/ionic level when HCl is added?

What is the role of the H+ and OH-?

List species that are present at the end.

PART 3: NH3(aq) + H2O(l) ---> NH(+1)(aq) + OH(-1)(aq)

observations:

1. when added phenolphthalein to test tube of ammonium hydroxide, a light purple/pink color was formed

2. when added HCl to it, the color changed back to clear and a cloudy gas formed over the solution in the tube.

3. when add NaOH, nothing happened but I think something should have. It just stayed a clear liquid and the gas had stopped.

What's the primary species present after HCl is added?

What happens on the ionic/molecular level when NaOH is added?

Whats the role of H-? OH-?

List all species present at the end.

Explanation / Answer

PART 1: Ca(+2)(aq) + 2OH-(aq) ---> Ca(OH)2(s)

3. HCl added to test tube with Ca(OH)2 and the solid Ca(OH)2 precipitate dissipated and the pink color changed back to white.

What happens to the OH- ions?

OH- ions react with H+. to form H2O (l)

Which OH- ions are reacting? the ones in the precipitate or in solution or both? How do you know?

Only those in solution can react with H+. all other must go into solution first in order to react. Note that OH- and H+ neutralizaiton must occur in aqueous solution

What happens at the moleulcar/ionic level as the HCl is added?

In the molecular leve, OH- from saturated solution will react with H+ from HCl. As OH- react, the shift goes from solid Ca(OH)2 to aqueous Ca+2 + 2OH- in order to counterbalance the loss in equilibrium

Finally, we could say that more solid will be able to dissolve in this solution, i.e. it is said to incrase solubilty of Ca(OH)2

What's the role of H+? Cl-?

The role of H+ is to neutralize, it will increase the solubility of Ca(OH)2 due to neutralization

Note that Cl- ions are just spectator inos, have nothing in special with this reaction. One could say that CaCl2 salt is formed as more neutralizaiton occurs.

List all species present at the end.

At the end,

Ca2+. OH-. H2O(l). Cl-

assume H+ ions to be pretty small due to OH. presence

Related Questions

Navigate

• Browse (All)
• Browse L
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.