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Chemistry 20 Online
OpenStudy (vera_ewing):

@JFraser @thomaster Please help!

OpenStudy (vera_ewing):

OpenStudy (jfraser):

rate is change in concentration over time, right? \[rate = \frac{\Delta[H_2O_2]}{\Delta time}\]

OpenStudy (vera_ewing):

Right. So I'm pretty sure the answer is A. Just need you to check.

OpenStudy (jfraser):

so find the change in concentration from the first time interval, and compare it to the change in concentration over the second time interval

OpenStudy (vera_ewing):

Well the first one is 6.7 x 10^-3 right?

OpenStudy (jfraser):

it's not

OpenStudy (jfraser):

the \(change\) in concentration is (2.0M - 1.6M), and the \(change\) in time is (300s - 0s)

OpenStudy (vera_ewing):

Ohhh.

OpenStudy (jfraser):

so the initial rate is\[\frac{1.6M - 2.0M}{300s - 0s}\]

OpenStudy (jfraser):

and the second rate is the change in concentration over the second time interval

OpenStudy (jfraser):

the rates do change

OpenStudy (jfraser):

you're jumping without thinking

OpenStudy (vera_ewing):

-0.4/300s ?

OpenStudy (jfraser):

that's the first rate, now find the second rate

OpenStudy (vera_ewing):

Can you tell me the formula for the second rate?

OpenStudy (jfraser):

finding rate is always the same formula, change in concentration over change in time

OpenStudy (vera_ewing):

-0.3/300s ?

OpenStudy (jfraser):

the "second" rate isn't the actual second time window, it's the second set they ask you about, the time from 1800s to 3000s

OpenStudy (vera_ewing):

0.72-0.15 ?

OpenStudy (jfraser):

that's the change in concentration, what's the change in time?

OpenStudy (vera_ewing):

1200

OpenStudy (jfraser):

properly it's (3000s - 1800s) but yes

OpenStudy (jfraser):

so\[rate_1 = \frac{1.6M - 2.0M}{300s - 0s}\] and \[rate_2 = \frac{0.15M - 0.72M}{3000s - 1800s}\] are the two rates equal?

OpenStudy (vera_ewing):

-0.4/300s and -0.57/1200s, no they're not equal.

OpenStudy (jfraser):

so simplify the fractions and pick the correct option

OpenStudy (vera_ewing):

Okay, so I got D. Is that correct?

OpenStudy (jfraser):

that's what I get

OpenStudy (vera_ewing):

Yay! Thank you so much! :)

OpenStudy (jfraser):

YW

OpenStudy (vera_ewing):

Can you please help me with this one? http://openstudy.com/study#/updates/555f3747e4b023a7e9bab817

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