Name Date Section Chemical Equilibrium Post Lab Questions 1. What does it mean f
ID: 588313 • Letter: N
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Name Date Section Chemical Equilibrium Post Lab Questions 1. What does it mean for a chemical reaction to be at oquilbrium? 2. In part 2 of this experiment, you used the indicator methyl orange. Why was this indicator chosen instead of phenolphthalein? Why is phenolphthalein not an appropriate indicator for this equilibrium? Considering part 4C in this experiment, give two other ions that could be added besides hydroxide that you might expect to have the same effect. (Hint: Use the solubility table in the "net ionic equations" exercise.) 3. properly called aqueous The lab manual mentions that ammonium hydroxide is more ammonia. Based on this, is NH, likely a strong base or a weak base? Would you predict the following equation to have a large or small Keq value? 4. NHs(aq) + HO (D NH4 (aq) OH (aq) Revised 1/17/17Explanation / Answer
1) When a reaction is at equilibrium, both the forward and reverse reactions take place at the same rate, and the concentrations of both the reactants and products remain constant.A reaction at equilibrium essentially means that the amount of reactants and products is constant (but not necessarily equal) and continue to be constant until a change is imposed on the system.
2) Methyl orange is used in strong acid vs weak base titrations because the end point of the titration is very low and therefore it is a better indicator than phenopthlein.
3) Need experiment details to write the ions like OH- (PO43-, CO32-)
4) Ammonia is actually considered to be a weak base due to it's inability to completely ionise in solution (consequently, it has a relatively low pH>7). Ammonia (NH3) will react with water to produce ammonium (NH4+) and hydroxide ions, however this reversible reaction will occur with only about 1% of the NH3 molecules, meaning you need a lot of NH3 to produce only some OH-. Keq value of the above reaction is very small.
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