[crays]

Hi, i'm a high school student having exam say ... 2 more months, and i still don't understand the chapter thermo chemistry.

In "Heat of Precipitation"
If a solution containing 1 mol of M+ ions reacts with 1 mol of sulphate ions (SO4 2-)
The volume are the same. and the increase in temperature is 5 degree. how do i determine the heat of precipitation ?

[kylon]

It is not enough info to solve the question...
Here you only got the change of temperature only...
You must have another 2 info. a) mass b) Specific heat capacity

[crays]

I'm sorry, here's the full question.
When 500 cm3 of 1.0 mol dm-3 solution containing M+ ions is added to 500 cm3 of 1.0 mol dm-3 solution containing SO4(2-) ions, the temperature of the solution increases by 5 degree celcius. What is the heat of precipitation of M2SO4 in the reaction ?

Specific heat capacity of water - 4.2 J g-1 degree -1

Thanks ~

[kylon]

When 500 cm3 of 1.0 mol dm-3 solution containing M+ ions is added to 500 cm3 of 1.0 mol dm-3 solution containing SO4(2-) ions, the temperature of the solution increases by 5 degree celcius. What is the heat of precipitation of M2SO4 in the reaction ?

Specific heat capacity of water - 4.2 J g-1 degree -1

Find change of heat,
mc*change of T = 1000*4.2*5J= 21kJ

Then find moles of M+ and SO4(2-),
MV/1000...
the moles of both are 0.5

heat of precipitation is 21/0.5 = -42kJ/mol
the negative sign is because the temperature is rising...

[crays]

I'm so sorry for the late reply.

Thanks alot for the solution. I understand most of it.
But i just want to know, do we have no do anything to the amount of moles ? I mean like M⁺  +  SO₄^2- will give you M₂SO₄ do we have to do anything to the number of moles of M⁺ ions or SO₄^2- ions ?

[kylon]

erm!!!
need help
some chemistry pro please help in the question above, i do a mistake!