ppm

[Hielly]

a sample of pond water contained 88.00 microgram g-1 of dissolved oxygen gas. calculate the amount in grams of dissolved oxygen in 4.00L of pond water.


thanks

answer says 0.352g

[fady_22]

As the density of water is equal to 1, the mass of water= volume of water. So, 4 L of water= 4000 g.
m(02)= 88*10^-6 g/g water *4000 (as 1 microgram= 10^-6 g)
        =0.352 g

[Hielly]

As the density of water is equal to 1, the mass of water= volume of water. So, 4 L of water= 4000 g.
m(02)= 88*10^-6 g/g water *4000 (as 1 microgram= 10^-6 g)
        =0.352 g

thanks i got the mass of water and solute, which is what you got. Then i subbed it in the c=mass/volume

would you say the concentration is 4000 ? from water. i got confused here

[samuch]

how did you get 4000?

[d0minicz]

4L = 4000mL = 4000g

[samuch]

yeah i get that part but for the concentration?

would you say the concentration is 4000 ? from water. i got confused here

[Hielly]

i used the formula C= mass of solute in grams/ volume of solution in litress

so now i find C and volume of solution in litres

volume of solution in litres is 88*10^-6

and C=?

is this the right way to do it?

ignore my question samuch, i made a mistake

[fady_22]

If you are doing it your way, then the concentration would be 88*10^-3 g/ L (you must change the concentration to g/L, by multiplying the concentration by 10^3, if using litres as the volume) and the volume would be 4.0L.
c=m/v
m=c*v
   =88*10^-3*4
   =0.352 g

[vcesuccess]

Our teacher likes to put what we know first then what we have and what we don't know to find out the quantity of unknown such as:
We have            100g in 1000mL
We want to know xg in 1542mL

Use cross multiplication to solve for xg