MODULE ANSWER

MODUL ANSWER

Preparation of a solution by dilution (pg 128)

1(a) Standard solution is a solution in which its concentration is accurately known.

(b)        -molar mass of NaOH = 23+16+1 = 40 g mol^-1

              - mol NaOH              = 500 × 1.0 /1000 = 0.5 mol

              - Mass of NaOH        = 0.5 mol × 40 g mol^-1= 20.0 g

Preparation of 500 cm³  1.0 mol dm^-3 sodium hydroxide

-          20.0 g                          weighing bottle

-          20.0 g                          distilled water

-          Volumetric flask

-          Rinse           distilled water   volumetric flask

-          Distilled water         volumetric flask                                calibration mark

-          Volumetric flask     stopper                                inverted

Calculate the volume of 1 mol dm^-3 sodium hydroxide used:

-          M₂  × V₂      = 0.1 × 250 = 25 cm³

M1                   1

Preparation of 250 cm³ 1.0 mol dm^-3 sodium hydroxide

-          25 cm³

-          25 cm³         volumetric flask

-          Distilled water         volumetric flask                                calibration mark

-          Volumetric flask     stopper                                inverted

1(a) (i) weak acid       : An acid that partially ionizes in water to produce low concentration of hydrogen  ion, H⁺.

Strong acid                  : An acid that completely ionizes in water to produce high concentration of hydrogen ion, H⁺.

(ii)

-          higher

-          stong acid                  completely                         higher

-          weak acid                  partially

-          CH3COO^-  +   H⁺

(iii)

-          higher                         lower

-          lower                          higher

b)

  -      molecules                  ionise                    molecules           molecules           neutral

   Hydrogen

-          ionises partially       ethanoate           hydrogen

2a(i) solution P

     (ii) solution U

b(i)         Q

(ii)         R

(iii)        T

(iv)       P

(v)        U

(vi)       S

c(i) P/Q/R and T/U

  (ii) P/Q

3.       80 g dm^-3

4.       0.5 mol dm^-3

5.       2 mol dm^-3

6.       10 g

7.       0.4 mol dm^-3

8.       50 cm³

9.       a)

Number of mol of sulphuric acid  = 50 × 1       1000  = 0.05 mol H2SO4 → 2H+ + SO42- From the equation, 1 mol of H2SO4: 2 mol of H+ 0.05 mol of H2SO4 : 0.1 mol of H+	Number of mol of hydrocloric acid  = 50 × 1       1000  = 0.05 mol HCl → H+ + Cl- From the equation, 1 mol of HCl: 1 mol of H+ 0.05 mol of HCl : 0.05 mol of H+
The number of H+  in 50 cm3 of 1 mol dm-3 of sulphuric acid is twice of the number of in 50 cm3 of 1 mol dm-3 of hydrochloric acid.
Sulphuric acid is diprotic acid whereas hydrochloric acid is monoprotic acid. 1 mol of sulphuric acid ionises to 2 mol of H+  whereas 2 mol of hydrochloric acid ionizes to 1 mol of H+ . The number of H+  in the same volume and same concentration is doubled in sulphuric acid compared to hydrochloric acid.

b) 100 cm³

preparation standard solution

Standard solution

•  A standard solution is a solution containing a precisely known concentration.

Methods of Preparing Salts

Methods of Preparing Salts

1.   The method used to prepare a salt will depend on its solubility in water, that  is, whether it is soluble or insoluble in water.

Q1.     Suggest suitable chemicals required to prepare the following salts and write down the chemical equations involved.

a.       Potassium nitrate

b.       Copper(II) sulphate

c.       Aluminium nitrate

d.       Iron(II) chloride
e.       Ammonium nitrate                       

PEKA 2 (TITRATION)

Topic :  Acids and Bases

                                                                             

Aim                           :To find the end point in the titration of hydrochloric acid and sodium hydroxide solution using an acid-base indicator

                                  

           

Materials                   :0.1 mol dm^-3 hydrochloric acid, 0.1 mol dm^-3 sodium hydroxide solution, phenolphthalein

Apparatus                :Burette, 25 cm³ pipette, pipette filler, retort stand and clamp, white tile, 250 cm³ conical flask

                                  

Procedure                 :                (Must draw the diagram and list out the procedure)

                                

Result                        :   

Titration set	Estimation	1	2	3
Final burette reading/ cm3
Initial burette reading/ cm3
Volume of hydrochloric acid needed/ cm3

 Discussion                :

Able to write the chemical equations for the reactions correctly    

Able to show the calculation

                                      Able to state a observation and inference  correctly

                                     

                                      Able to state precaution

Conclusion                :