Question

"Is it important that the concentration of HCl is exactly 2 M?if a .25 g sample of magnesium metal is used would 1.9 M HCl or 2.1 M HCL work just as well? will the heat of reaction measured be the same for all three concentrations? Explain why or why not"

Answer 1

My guess is that all 3 molarities would be fine, because they will all be enough to react all of the Mg.

Answer 2

My guess would be the higher molarity would produce more heat because diffusion is happening at a more rapid pace. Think about it. Heat is just a measurement of the average kinetic energy (which is movement). So a higher concentration would have more collisions going on and would thus produce more heat.

Another way to think about it is to think about the extremes. Would 12 M HCL be any different than .0001 M HCL? Uh you betcha. So, yes, concentration is extremely important.

Answer 3

Thank you. I didn't think that the speed of the reaction would affect the heat produced. I know the heat given off in exothermic reactions is the result bonds breaking and forming. And I know 12 and .0001 are different. What I meant was that at the quantity being used, there would be enough 1.9, 2, or 2.1 M solution to react .15 grams

Answer 4

I understand your question now. Let me do a bit of review through my chemistry notes and I'll give you a better answer.

Answer 5

I was taught that concentration affects reaction rate with only 2 exceptions.

Answer 6

heat is related to speed! therefore, you know by your lovely formula that you have in your book, that more energy equals more disaster. to increase the speed, increase heat. to reduce, lower the temp.
and since they have movement (or motion), they will have kinetic energy. hence, the particles will not all have the same energy, and the energy of the particles is constantly changing as they undergo changes in speed.

Answer 7

I think the formula is \(E= \frac{1}{2}mv^2\)

Answer 8

It's PV = nRT

Answer 9

specific head is \(Q = mc\Delta T\)

Answer 10

I see. I thought T would account for the speed. But still we agree that concentration does affect the rate of reaction.

Answer 11

that formula is only good for ideal gases. in real life, most gases do not fit under "ideal gas"

Answer 12

i was referring to your formula of ideal gas law: PV=nRT

Answer 13

In response to my two exceptions rule stated earlier, the two exceptions were:
1) Where a catalyst is already working as fast as it can (we can eliminate this since you do not have a catalyst). Btw catalysts do not get consumed ever.
2) In certain multi-step reactions (where a rate determining step is governing the overall reaction rate).
Neither is the case for this question.

Answer 14

actually, i havent even read the question, i just saw that you were discussing heat and speed.

Answer 15

thanks guys for all this help, sorry I fell asleep before the discussion started.