chem notes

1. Prepared by;
Punia Turiman
For Chemistry HL Year 1 2011/13

2.  A homogeneous mixture formed from a
solute and a solvent.
 Solute : substance that dissolves in solvent
 Solvent : liquid present in excess in which
dispersion occurs

3. gdm-3 Moldm-3
Mass of solute in g No.of mole of solute
1 dm3 of solution 1 dm3 of solution
e.g. e.g
Calc. the conc. of a Calc. the molarity of
0.0400 moldm-3 0.4 moles of NaOH in
solution of sodium 500 cm3 of water.
carbonate, Na2CO3,
in gdm-3.

4.  Question : Calculate the mass of NaOH needed to
prepare a solution of 250.0 cm3 of 0.500 M
solution?
 Answer :
 n = mV/1000
= 250.0 (0.5000) = 0.1250 mol
1000
Mass of NaOH = n x Mr
= 0.1250 x (22.99 + 16.00 + 1.01)
= 4.999g

5.  A solution is made containing 2.38g of MgCl2
in 500 cm3 of solution.
 a) What is the conc. of MgCl2 in this solution?
 b) What is the conc. of the chloride in this
solution?

6. 3
100cm3 400cm New
of of
conc.
0.500M 2.00M
HCl HCl of HCl??

7. 100 cm3 Diluted New
of 0.1 in 400
cm3 of conc.??
moldm-3
NaOH pure
water

8. A titration is a lab procedure
where a measured volume
of one solution (burette) is
added to a known volume &
concentration (flask) of
another solution until the
reaction is complete.

9.  A standard is a solution of precisely known
concentration
 It must be available in a highly pure state
 It must be stable in air
 It must dissolve easily in water
 It should have a fairly high relative molecular
wt
 It should under go a complete and rapid
reaction

10. 25 cm3 of NaOH aq. required 28 cm3 of 1M H2SO4
aq. for complete neutralization.
 Write a balanced eqn. for the rxn.
 How many moles of the acid were used to neutralize
the NaOH?
 How many moles of the alkali were neutralized?
 How many moles of the alkali are there in 25 cm3 of
solution?
 What is the molarity of the sodium hydroxide?

11.  27.82g of hydrated sodium carbonate crystals,
Na2CO3.xH2O were dissolved in water and made up to
1.000 dm3. 25.00cm3 of this solution were neutralized by
48.80 cm3 of HCl of concentration 0.1000 moldm-3.
 Write eqn. btw. Na2CO3 and HCl
 Calc. the conc.of Na2CO3 neutralized by HCl
 Determine mass of Na2CO3 neutralized by HCl and hence
the mass of Na2CO3 present in 1.000dm3 of soln.
 Calc. mass of water in the hydrated crystal and hence fine
the value of x. (IBO2004)

12. Try ALL questions.
Practice makes perfect.