Question

Calculate concentration using graph

Answer 1

where is the graph?

Answer 2

sorry thought i attached it

Answer 3

tell me the year and variant of the paper
its IGCSE chem paper 6 right?

Answer 4

i dont know the year or module i just got send the pic for revision from a friend

Answer 5

draw a line
from 30 degrees going vertically up till it reaches the curve line

Answer 6

then, when u reach the curve by going vertically,
now go horizontally to the left to reach the Y axis

Answer 7

like this http://prntscr.com/6jxlmy kind of

Answer 8

then that value will be your concentration but in different unit
so now we gotta convert it to appropriate units

Answer 9

yeah that gives me 0.155 but is this the concentration???

Answer 10

no not yet

Answer 11

g/cm3 is not conc

Answer 12

conc = mole / volume
and lest replace mole with its formula which is
mole = mass / Molecular mass
so now
\[\sf conc = \frac{ mass}{ Molecular~mass \times volume }\]

Answer 13

so taking a close look at formula all you need to do is multiply the value from graph by
1/ molecular mass
because
\[\sf conc = \frac{ 1 }{ Molecular~mass } \times \frac{ mass }{ volume }\]

Answer 14

and then multiply what you get by the value u got from the graph

Answer 15

so i do 1.55 times \[\frac{1}{ 74 }\]

Answer 16

because 74 is the mr

Answer 17

or wait

Answer 18

just leave it be 1/74
but now the g/cm3 value divide by 1/1000 first
this way its more clear that you are converting cm3 to dm3

Answer 19

sorry my error*

Answer 20

but 74 is the mr and the mr isnt in cm3 so i dont understand, isnt c=n/v where n is number of moles

Answer 21

wait i'll say it in different way

Answer 22

1/74 leave it be
this is to multiply by g/dm3 value

but now there is a problem
your value is g/cm3
thus we need to change cm3 to dm3

Answer 23

\[\sf g \div \frac{ cm^3 }{ 1000 }\]
which changes to
\[\sf \frac{ g \times 1000 }{ cm^3 }\]

Answer 24

so multiply your graph value by 1000 to change it to g/dm3
is it clear so far?

Answer 25

no, i doing understand where the cm3 is coming from, if the graph value is g then what value is the cm3???

Answer 26

*dont

Answer 27

oh god im so sorry
its 100cm3 http://prntscr.com/6jy05f

Answer 28

ha dont worry

Answer 29

im reaaaaally sorry i'll show it again using this correction now
\[\sf \frac{ g \times 1000 }{ 100 ~cm^3 }\]
and cancelling zeros in 1000/ 100 = 10
so just multiply your graph value by 10 instead

Answer 30

and only then multiply the result by 1/74

Answer 31

so 1.55*10*1/74

Answer 32

yes

Answer 33

so thats a concentration of 0.209 mol dm3, thanks for your help!!!

Answer 34

yeah i hope i didnt miss any point this time >_< sorry about that huge error