i need help with titration?

Question

basically i need to do some stuff on titration...

i need to find the concentration of sulphuric acid and i am given sodium carbonate as the base....

what do i do?

and whats the balanced equation - because i need to find the amount of Na2CO3 that will be need - how do i do that? - i need a balanced equation right???

thanks a million

Answer 1

If you are going to calculate the concentration of the sulfuric acid. You need to know the following equation

N (normality) = (weight of Na2CO3 (g)) X 1000 / [ (mL of acid) x (53 - the equivalent weight of Na2CO3) ]

And remember 1 N H2SO4 = 0.5 Molar H2SO4

Answer 2

Balanced equation:-
H2SO4 + Na2CO3 = Na2SO4 + CO2 + H2O
Note that the molar ratios are all 1:1 :: 1: 1 : 1
Proceedure
Dissolve a known mass of Na2CO3 in 25 cm3 of distilled water - approximately 2 grams. - in a volumetric flask and make in to 250 cm3.
Find the Conc'n:-
1st. Mr of Na2CO3 =
2 x Na = 2 x 23 = 46
1 x C = 1 x 12 = 12
3 x O = 3 x 16 = 48
Add 46 + 12 + 48 = 106 (Mr of Sodium carbonate).
2nd. Find moles of Na2CO3 - I am assuming a mass of exactly 2.12grams.
Mol(Na2O3) = 2.12 / 106 = 0.02 mol(Na2CO3)
is contained in 250 cm3.
therefore Conc'n is 250cm3 x 4 = 1000cm3 (1 dm3)
0.02mol x 4 = 0.08 mol
and 0.08 mol is contained in 1 dm3. So conc.n is written as
0.08mol/dm3
Take a 25cm3 aliquot from the volumetric flask and place it in a conical flask, together with a few drops of universal indicator.
So moles(Na2CO3) is = (25 cm3 x 0.08 mol/dm3) / 1000cm3
- do - = 0.002 mol.
From the molar ratios above 0.002 mols (H2SO4) is needed to react exactly with 0.002 mols (Na2CO3)
Titrate from a burette the H2SO4 until the indicator is red.This must be done drop-by-drop.Do several titrations and take a mean titration for the calculation .
If say 22.25 cm3 of (H2SO4) is titrated through then conc'n can be calculated.
Conc;(H2SO4) = (0.002Mol x 1000cm3) / 22.25cm3
- do - = 0.8988764 moles/dm3
Usually written to 2 d.p. as 0.90 mol/dm3

Answer 3

Na2CO3 + H2SO4 = Na2SO4 + H2O + CO2gas

Find the atomic weights of Na, C, O, S and calculate the molecular weights of Na2CO3 and H2SO4.

The H2SO4 is unlikely to be stronger than M(olar), ie the molecular weight in gm dissolved per litre of solution. Make your sodium carbonate solution, say 1.5M.

Pipette exactly 10ml of carbonate solution into a conical flask. Add a few drops of indicator, eg phenolphthalein. The acid goes in the 25ml burette, to exactly the 25ml mark, read for non-parallax.

Run the acid rapid dropwise into the flask with constant swirling and stop the flow occasionally until effervescence subsides. At some point the indicator will change colour locally as the acid temporarily neutralises all the local base. Stop the acid and swirl until the colour change disappears. Continue adding the acid more slowly until with one drop the colour change becomes universal and permanent. This is the point of neutrality.

Refill the burette and repeat the titration twice more with clean glassware and take the average of the three readings.

Since the strength of the base is known and both chemicals are 'dibasic' the strength of the acid is in the ratio of x ml of acid used to neutralise 10ml of base, i.e 10/x.

Should the burette run out of 25 ml acid before the neutral point is reached in the first titration, the base is too strong. Dilute the base solution exactly in half and repeat the titration until you get a neutral point within 25ml of acid. When you have carried out the three titrations to get an average don't forget to divide the 10/x concentration by half to compensate for diluting the base; eg.

Assume it takes 15ml of acid to neutralise 10ml of base. The base is 1.5M (1 Molar) therefore the acid is 1.5 x 10/15 = 1 Molar. Use the molecular weight of sulphuric acid to convert 1M to g per litre.

Answer 4

Ok don't panic, i'll try to explain things.

First of all you need to know the concentration of the Sodium carbonate, in Moles/dm3. Let's say it is "x"mol/dm3.

The you must know the equation of the reaction between sodium carbonate and sulphuric acid:
H2SO4 + Na2CO3 gives CO2 + H2O + Na2SO4. this equation is balanced (see for yourself)

Now...when you did your titration in the lab, you had sulphuric acid in the conical flask and sodium carbonate in your burette. Get the average of the titre values you got in the lab, let's say they are "Y" cm cubed of Na2CO3.

The volume of sulphuric acid that you used is "z" cm cubed.

then...(follow closely)...have a good look at the equation. The number of moles of sodium carbonate is the same as the number of moles of sulphuric acid, as the are in the ratio of 1 : 1. It is crucial that you realise this concept.

so then you must say: In 1000cm cubed, there were X moles of Na2CO3, so how much in Y cm cubed? Let's say the answer was X".

Then you say: the ratio of H2SO4 : Na2CO3 is
1 : 1
therefore X" : X"
therefore: there were X" moles of H2SO4 in Z cm cubed.

if X" moles H2SO4 in Z cm cubed, then how many moles in 1000cm? This gives you the concentration in Molarity (mol/dm cubed) of sulphuric acid.

Print this answer, get your practical sheets and work this out step by step. It might take you time to realise the concept, but once you get it right, you'll always get it right.

Answer 5

all these answers are long. firstly try your book.

work out and balance the equation. should be 1:1:1:1.

then work out the moles of sodium carbonate by using:

mass/molar mass.

as it is 1:1,

use the equation:

moles of Na2CO3 = V/1000 x C

where V = volume of sulphuric acid (should be given in cm cubed) and C is conc of solution in M.

rearrange the equation to get:

(moles x 1000) divided by volume which equals C.

hope it helps!

Answer 6

First is the balanced equation:
H2SO4 + Na2CO3 -----> Na2SO4 + H2O + CO2

The most important thing to note is that one mole of sulphuric acid neutralises one mole of sodium carbonate.

Use the equation concentration = moles / volume (in litres)

to find the moles you do the mass of substance divided by its RFM
There are 1000cm3 (ml) in a dm3 (litre)

Use this site for more info:
http://www.scienceaid.co.uk/chemistry/analytic/titration.html
and
http://www.scienceaid.co.uk/chemistry/fundamental/substance.html

Answer 7

ofcourse you need that,, to calculate the number of moles you needs of each reagent and convert the to mg/l