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*-._♥ g O r g E o U s ~ B o O ♥_.-* (purplecaphootie) wrote in homework,
@ 2003-05-04 13:38:00
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    Current mood: frustrated
    Current music:Emotions in me

    URGENT HELP ME PLSSS!!!
    *Sigh* okay, i need help with this please please please....

    Question:

    To make up the weaker solutions, what volume of the 80 micro M nickel solutions and what volume of nutrient solution should you add together to make

    a) 1 liter of 20 micro M (moles) nickel solution?
    b) 1 liter of 5 micro M nickel solutionm?
    c) 1 liter of 0.5 micro M nickel solution?

    i need three answers...each on A,B, and C...

    nutrient solution : 25 ml
    Atomic weight of Ni = 58.7
    CL= 35.5
    O = 16
    H 1

    thats the only numbers given... they said its about dilution but i dont know how...or i forogot and i need to hand this assesment in by the 16th of may pls help me pls!!! pls!!! pls!!! =,(



(Post a new comment)


claudiusmaximus
2003-05-05 20:42 (link)
Take X ml of the 80 micro M nickel solution and Y ml of the nutrient solution.

The total volume V = X + Y ml.

The concentration C = 80 X / (X + Y) micro M.


So for question A, V = 1000 and C = 20, so you have the equations:

X + Y = 1000
80 X / (X + Y) = 20

which are equivalent to

X + Y = 1000
20 X + 20 Y = 80 X

which are equivalent to:

X + Y = 1000
3 X = Y

and substituting the second equation in the first you get

4 X = 1000

so X = 250 ml and Y = 750 ml


The same method works for B and C too, you just need to put different numbers in.

(Reply to this) (Thread)


purplecaphootie
2003-05-06 03:05 (link)
do i subtitiute the C (20) to the other numbers like, 5 and 0.5? is that the only one ill substitute? not the 1000?

thanks so much by the way your a big helppppppppp!!!!!!

(Reply to this) (Parent) (Thread)


claudiusmaximus
2003-05-06 03:35 (link)
Yep that's right, V is 1000 for all just change C.

(Reply to this) (Parent) (Thread)

Re:
purplecaphootie
2003-05-06 03:44 (link)
thanksss soo much!!!

(Reply to this) (Parent) (Thread)


purplecaphootie
2003-05-06 05:59 (link)
i just want to ask how you got 3x on the equation you wrote (3rd equation : 3x = y)

(Reply to this) (Parent) (Thread)


purplecaphootie
2003-05-06 06:06 (link)
sorry dont need to reply i got it already...thanks

(Reply to this) (Parent) (Thread)


claudiusmaximus
2003-05-06 09:12 (link)
oops, didn't notice this, i replied straight from the emal. sorry

(Reply to this) (Parent) (Thread)


claudiusmaximus
2003-05-06 09:11 (link)
20 x + 20 y = 80 x
subtract 20 x from both sides
20 y = 60 x
divide both sides by 20
y = 3 x

(Reply to this) (Parent) (Thread)


purplecaphootie
2003-05-06 09:13 (link)
thanks, got it already.... =) thanks for your help

(Reply to this) (Parent) (Thread)


purplecaphootie
2003-05-06 06:34 (link)
last last question...im sorry if your annoyed already....
how did you get 4X in 4X = 1000
is it because the 3X = Y and Y represents 1? and just add it to 3x so it will be 4x? am i right?

(Reply to this) (Parent) (Thread)


claudiusmaximus
2003-05-06 09:20 (link)
two equations
x + y = 1000
3 x = y

the second equation tells you what y is, so put it into the first one

x + 3 x = 1000

and x = 1 x so you have

1 x + 3 x = 1000

and by a property of addition and multiplication called distributivity

(1 + 3) x = 1000

so

4 x = 1000

then divide both sides by 4

x = 250

and from the equation

x + y = 1000

substitute the value of x

250 + y = 1000

subtract 250 from both sides

y = 750


(you could use the other equation to find y:

3 x = y

substitute x

3 250 = y

evaluate 3 250

750 = y

)


This is good practice for my algebra, we have to do stuff like this, and explain why we can do every single step from the basic properties of the number system (or other more abstract systems). I got my library card today so next week I'll be going there every day to learn algebra :-)

(Reply to this) (Parent) (Thread)


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