A)A + 3B 2C What is the average rate of the reaction with respect to A over the

Question

A)A + 3B 2C

What is the average rate of the reaction with respect to A over the first 15 seconds of the reaction in M/s? (Express your answer as a decimal, not scientific notation and be mindful of significant figures)

B)At a certain time in a reaction, substance A is disappearing at a rate of 4.0 x 102 M/s, substance B is appearing at a rate of  2.0 x 102 /s, and substance C is appearing at a rate of 6.0 x 102 /s.

Select the correct stoichiometry of the reaction being studied.

2A + B 3 C

4A   2B + 3C

2A   B + 3C

A + 2B   3C

A   2B + 3C

Explanation / Answer

A)

Given a reaction:

aA+bBcC+dDa

rate of reaction = 1/a x [A]/t

since 1/a = 1

rate = -[A]/t

rate = - (0.75 - 0.5)/15 - 0

rate = - 0.25/15 = 0.0167 M/s

So average rate of the reaction = 0.0167 M/s

B)

A is disappearing at a rate of 4.0 x 102 M/s, substance B is appearing at a rate of  2.0 x 102 /s, and substance C is appearing at a rate of 6.0 x 10-2M/s.

So only A is disappearing and B and C are appearing Now C is appearing 3 times as faste as B and A is disappearing twice as fast as B so the correct molar stoiciometry is 2:1:3 between A disappearing B appearing abd C appearing

So the correct equation should be

2A   B + 3C

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