AS Chemistry question (again) - sorry

OP

mik1a

g dm^-3 isn't a concentration! :confused:

I copied it from a worksheet.
If it helps, the answer is 1.755gdm-3

Reply 3

visesh

17

mik1a

g dm^-3 isn't a concentration! :confused:

It is. It's not as "clean" as moldm^-3, but it is mass/volume. Think of it as the "density" of a solute in a solution, and therefore a concentration.

Reply 4

1)work out the moles of Agno3 = conc. * (volume/1000)
2)equation for reaction gives the number of moles of NaCl
3) concentration of NaCl=moles NaCl/volume(you might need to divide the vol by 1000 to get in dm^-3)
try that?

Reply 5

OP

I still don't understand. Can someone show me the workings?

Reply 6

Widowmaker

I still don't understand. Can someone show me the workings?

do you know the equation for the reaction ie
Nacl + Agno3--->
if u no that then perhaps i can help alittle better

Reply 7

OP

littleone

do you know the equation for the reaction ie
Nacl + Agno3--->
if u no that then perhaps i can help alittle better

Yes, it's
NaCl + AgNO3 --> NaNO3 + AgCl

Reply 8

OP

Chemistboy are you there?

Reply 9

i got 17.55. let me try agin

Reply 10

OP

littleone

i got 17.55. let me try agin

The answer says 1.755gdm-3. I really don't get this one question.

Reply 11

Widowmaker

10 cm3 of a solution of NaCl react with 15 cm3 of 0.02 M silver nitrate solution. What is the concentration of the NaCl solution in g dm-3?

i think maybe the answer is wrong...
if you look at the equation, it is a 1:1 ratio
which means the number of moles of AgNO3 equals that of NaCl
then i guess you'd re arrange conc=moles/volume to get the number of moles
then use that anser in the same equation to get a concentraion
and i reaaly dont get 480 for that
is this what you did?
sozzy i havent been of much help :frown:

Reply 12

OP

littleone

i think maybe the answer is wrong...
if you look at the equation, it is a 1:1 ratio
which means the number of moles of AgNO3 equals that of NaCl
then i guess you'd re arrange conc=moles/volume to get the number of moles
then use that anser in the same equation to get a concentraion
and i reaaly dont get 480 for that
is this what you did?
sozzy i havent been of much help :frown:

No the answer is 1.755gdm-3
I typed the wrong one.

Reply 13

heres wat i did to get 17.55 maybe u can see where ive gone wrong
1:1 ratio
moles AgNO3= concentration * Volume
this equals the moles of NaCl =0.3

then into moles=mass/RelativeFormulaMass
ie.
0.3=mass/58.5
mass=17.55

Reply 14

OP

It's okay, i've worked it out.

moles=0.02*15

Widowmaker

It's okay, i've worked it out.

how? well done btw!

Reply 17

OP