Question 5 photosynthesis is estimated to produce an average...

QUESTION 5 Photosynthesis is estimated to produce an average of 300 grams (dry weight) of plant matter per square meter, of which 40% is carbon. a) Calculate the total grams of carbon fixed each year by an area of 1432 square meters. (5) b) Of the glucose produced, 35% is used by the plant to fuel respiration; the rest is converted to plant matter. Given the answer from part (a) above, calculate the total moles of glucose produced annually by an area of 1432 square meters. (5)

Transcript

00:01 This is a sort of long problem, but it isn't too hard.

00:03 We're given some information about carbon dioxide.

00:07 We're asked to consider the photosynthesis reaction, and then to compare the energy produced per year via photosynthesis on land mass to the energy produced by nuclear power plants.

00:20 Here's some information that we're given.

00:25 The net amount of co2 fixed by photosynthesis on the land mass of earth is 5 .5 times 10.

00:33 To the 16th grams per year.

00:40 We're going to assume all of this is converted to glucose, according to this reaction.

00:51 I'm pretty sure i used water here because it should be water.

00:59 Everybody knows how to balance this equation.

01:06 I'm using an s there because that was available, that was the heat of formation available in appendix c.

01:18 There we go.

01:20 Part a asked us to calculate, the energy in kilojoules per year.

01:36 In order to do this, it's going to be a two -part problem, two primary parts.

01:40 First, we're going to use hessus law to get the heat of the reaction, and then we're going to use, whoops, number two, then we're going to use strykeometry.

01:59 Pretty simple.

02:01 Let's do it.

02:04 I'm going to write the values up here.

02:11 These are in kilojoules per mole.

02:18 Water is 285 .83.

02:22 Again, kilojoules per mole.

02:24 And i'm not going to write that one there.

02:28 I've got to grab my stuff here.

02:36 And glucose is negative 2361.

02:47 Why did i think it was 236 .1.

02:50 But it isn't.

02:55 No, it is.

02:56 It is not right.

02:57 That is not right.

02:57 It is negative 1 ,273 .02, also kilojoules from all.

03:05 And don't forget, heseslaw is products minus reactants, some of the products minus some of the reactants.

03:12 So for the reaction, we'll have our product, which is, there's only one glucose there, 1 ,273 .02, that's kilojoules per mole, minus, take the coefficient, times, negative 393 .5, killedjols per mole.

03:38 And we'll add to that the 6 times negative 285 .83.

03:45 Again, kilogels per mole.

03:46 I forgot a negative up there.

03:50 Do the math on this, and i would pause and go ahead and make sure you get the math correct on this one.

03:56 I got positive 20802 .96.

04:11 And that's kilojoules per mole of glucose.

04:19 Then the second part of this is to use our stoichiometry.

04:22 Let me switch colors.

04:27 And we were given 5 .5 times 10 to the 16th grams per year.

04:38 We're going to convert grams 44 .01 grams per mole.

04:43 These are both co2...