https://padlet.com/loon_hui_jun/260lqw9hsz0j Please be CLEAR in your question. Needless comments would be deleted/ignored. en-us 2017-04-26 09:14:37 UTC 2017-08-06 16:11:29 UTC hello@padlet.com loon_hui_jun https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/171383023 Double click & type your question in the box created. 

Pls be clear and polite. :)
Needless comments would be deleted/ignored. ]]> 2017-05-11 23:33:09 UTC https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/171383023 https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178107671 May i ask how do we determine which point to cut on the x axis when drawing the tangents?
Ans: To find order w.r.t. [OH^-], we need to compare the rate of the 2 graphs when [RBr] remains constant. So we draw a tangent at the point where both graphs share the same [RBr]. The most convenient point (to draw tangent) is at time t=0 where both share [RBr]=0.0160 mol dm^-3]]> 2017-07-05 13:20:50 UTC https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178107671 https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178189933 May i ask will the gradient value determined for the rate be different?
Ans: The gradient depends on the tangent drawn (if its properly drawn). There would be a range of acceptable values for the gradient.]]> 2017-07-06 12:43:04 UTC https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178189933 https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178190736 Could you show us how you found out the half life for the curve where the concentration of OH- is 0.20?
I did not get constant half lives :(
Ans: Ah.. do not fret. Experimental data is simply experimental. So it's usual to meet with half-lives which are close enough but not exactly the same values. And we take the average of the two 2 half lives and conclude half lives are approximately constant. (average of non-successive half-lives of 100s and 94s = 97s)]]> 2017-07-06 12:54:04 UTC https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178190736 https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178204217 I don't even know how to place the ruler to draw the tangent
Ans: Maybe this would help? https://www.youtube.com/watch?v=EO0RhBS64YA&t=7s (until 2min 15s). It's advisable to use a transparent/see-thru ruler, like in video so you can see that the tangent only touches curve at that one point & draw tangent using a pencil. Calc gradient using the x and y intercepts will be faster. 

If you find better videos, pls update us too!]]> 2017-07-06 15:50:37 UTC https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178204217 loon_hui_jun https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178486991 2017-07-11 14:39:24 UTC https://padlet.com/loon_hui_jun/260lqw9hsz0j/wish/178486991