You will use the following graph to answer these questions: Part #1: Which of th

Question

You will use the following graph to answer these questions:

Part #1:

Which of the following represents how to calculate an average rate?

  A) Concentration/Time

B) Time/Concentration

C) Change in Concentration/Change in Time

D) Change in Time/Change in Concentration

Part #2:

Using the graph above, calculate the approximate change in concentration of NH3 from 50. seconds to 100. seconds. Pay careful attention to the sign of your answer. Enter your ansewr in units of M/s.

Part #3:

How does the rate of H2 compare to the rate of NH3. Hint, balance the reaction.

A) Rate H2 = -Rate NH3

B) Rate H2 = 2 * Rate NH3 /3

C) Rate H2 = 3 * Rate NH3? /2

D) Rate H2 = -2 * Rate NH3 /3

E) Rate H2 = -3 * Rate NH3? /2

Part #4:

Given your average rate of NH3 in part 2, calculate the average change in rate of H2 over the same time period. Again, pay careful attention to the sign.

Explanation / Answer

Part 1. In general terms, we usually put the y axis over the x axis, so option B and D can be discarted.

Now to an average rate, following the general equation of a slope:

m = y2 - y1 / x2 - x1

We can use something similar to this to calculate the rate average of this graph. So the correct option would be C.

PArt 2. Following the answer of the above part, the change of concentration during this time (I'll assume some values since we don't have the exact values at the times given):

t1 = 50 s M1 = 1.5 M

t2 = 100 s M2 = 0.75 M

Change = 0.75 - 1.5 / 100 - 50

change = -0.015 M/s

Part 3. The overall reaction is:

N2 + 3H2 -------> 2NH3

So the ratio of H2:NH3 would be

moles H2 / moles NH3 = 2/2

moles H2 = 3moles NH3 / 2

So the rate would be: Rate H2 = 3/2 rate NH3

PArt 4.

Finally, if we know that for NH3 the rate is (-0.015 M/s) then for H2:

H2 = -0.015 * 3/2

H2 = -0.0225 M/s

Hope this helps

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