Question

A student performs the reaction shown below.
NaOH + HCl → NaCl + H2O
She increases the concentrations of NaOH and HCl, and finds that NaCl is produced much more quickly. Which explains the outcome of her experiment?

NaOH and HCl molecules collide more frequently at higher concentrations. (I think it's this one)

NaCl requires a high concentration for any reaction to occur.

HCl acts as a catalyst, but only at high concentrations.

The higher concentrations create a higher temperature in the solution.

Answer 1

I don't know the chemistry too well. But I think I agree with you.

A catalyst is not used up in a reaction, but HCl is used (it's not on both sides of the equation in its entirety).

The NaCl reaction did occur before. Also, it would happen in a less concentrated solution.

As for the temperature, it would be the reaction that would produce the heat. From what I remember, that's not a very hot reaction.

And the first option is completely true. And I think it's fitting.

Answer 2

My memory tell me that the product is very warm indeed.
But the last option still isn't right.
Higher concentrations do create a higher temperature in the solution because more energy is released from the reacting particles. However i dont think this is the answer because temperature wasn't measured in the experiment.
The first option makes the most sense

Answer 3

Yeah, the increased heat would come from the increased number of reactions. That heat can \(then\) increase the rate of the reaction, but the difference from the temperature the first experiment to the second could only happen because of the increased frequency of reactions.

Is that right, @UnkleRhaukus ?

As for the heat of that reaction, I'm sorry! I'd go with UnkleRhaukus on that one. It just rings a bell for me, and it was years ago that I last did that. I might have been dealing with smaller concentrations, too.

Answer 4

yes,@theEric

Extra temperature will mean the particles are traveling faster, and hence bump into each other more often, thus the reaction rate will increase.

Similarly, more particles in the same space which are going to bump each other more frequently and hence react quicker.

Answer 5

The other reason i like the first option better than the last, is that the last option (unless you know the kinetic theory) isnt really an explanation.

Answer 6

Thanks guys :)