ACID-BASE REACTIONS

Week:                                                                   Date:                                                     Time:

Period:                                 Duration: 1 HR 20 MIN.                                                  Average age of learners: 16YEARS

Subject:                               CHEMISTRY                                                                         Class: SS TWO

Topic:                                    ACID – BASE REACTIONS

Sub topic:

Reference materials:

(1) ESSENTIAL CHEMISTRY, TONALD PUBLISHERS, I. O ODESINA

(2) NEW SCHOOL CHEMISTRY, AFRICAN FIRST PUBLISHERS, OSEI YAW ABABIO

(3) INTERNET

Instructional materials: beaker, beam balance

Entry behavior: The students have been density.

Behavioural objective: At the end of the lesson the students should be able to:

1.       Define mole.

2.       State the relationship between relative densities and relative molar mass.

3.       Solve problems relate to mass- volume relationship

CONTENT

 

ACID – BASE REACTIONS

An acid-base titration is an experimental procedure used to determined the unknown concentration of an acid or base by precisely neutralizing it with an acid or base of known concentration. This lets us quantitatively analyze the concentration of the unknown solution. Acid-base titrations can also be used to quantify the purity of chemicals, and calculate molar mass, molar concentration, mass concentration. Number of ions/particles of crystallization and solubility product.

 This is shown by a colour change in the resulting solution or in an added indicator. The main reason why indicator was used is to determine the end point of the titration or neutralization point or equivalence point.

INDICATOR

RANGE

ACID

ALKALI

AT END POINT

ACID/BASE

Litmus

5.0 – 8.0

Red

Blue

Purple

Strong acid and strong base

Methyl orange

2.9 – 4.6

Pink

Yellow

Orange

Strong acid and weak base or trioxocarbonate (iv)

Methyl red

4.4 – 6.3

Red

Yellow

Red

Strong acid and strong base

Phenolphthalein

8.3 – 10.0

Colourless

Pink

Colourless

Strong base and weak acid

No suitable indicator for titration of weak acid and weak base. Any indicator could be used for strong acid and base.

There are only seven (7) strong acids:HCl, HBr, HI, H2SO4, HNO3, HClO3, HClO4

There are only eight (8) strong bases:LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

Example of weak acids are acetic acid, hydrocyanic acid, HF, oxalic acid, ethanoic acid while weak bases are Ammonia, magnesium hydroxide, pyridine, sodium carbonate, potassium carbonate.

                Some materials used during acid-base titration and precautions in using some of them:

1.       Weighing bottle                                                2. Burette                            3. Retort stand

4.       Chemical balance                             5. Filter paper                    6. Funnel

7.       Pipette                                                                 8. White tiles                      9. Standard volumetric flask        10. Conical flask.

Precautions in using:

(a)    Pipette

i.                     Rinse the pipette with the solution . it is used to measure i.e base.

ii.                   Avoid air bubbles in the pipette

iii.                  Do not blow the last drop on the pipette.

iv.                 Make sure that the mark to be read is at the level with your eye.

(b)   Burette

i.                     Rinse the burette with acid or allow it to drain after rinsing with distilled water.

ii.                   Make sure that the burette jet is filled.

iii.                  Avoid air bubbles in the burette.

iv.                 Make sure the burette is not leaking.

v.                   Remove the funnel before taking your readings.

vi.                 Avoid inconsistent burette reading

vii.                Take your burette readings with your eyes at the same level as the meniscus to avoid error due to parallax

viii.              Clamp the burette vertically

 

 

(c)    Conical flask

i.                     Do not rinse it with any of the solutions used in the titration but with the distilled water.

ii.                   Wash down with distilled water any drop of the solution that stick by the sides of the conical flask during titration.

Standard solution is a solution of known concentration. The concentration of a solution in mol dm3 is the molar concentration.

A molar solution of a compound is one which contains one mole or the molar mass of the compound in one dm3 of the solution.

Mass concentration(gdm-3) = molar concentration (moldm-3) x molar mass (gmol-1)

Example

What mass of anhydrous sodium trioxocarbonate (iv), Na2CO3, present in 500cm3 of 0.1 mol dm-3.

Solution

Molar mass of Na2CO3 = 2Na + C + 3O

                                           = (2x23) + 12 + (3x16)gmol-1  = 106gmol-1

Volume = 500cm3  = 0.5 dm3 , molar concentration = 0.1 mol dm-3

Amount(mol)  = molar concentration (moldm-3) x volume (dm3)

                                =  0.1 mol dm-3  x  0.5 dm3 = 0.05 mol

Amount  =

Mass = amount x molar mass

          =  0.05 mol x 106gmol-1 = 5.3g

PRESENTATION

i.The teacher explains mole and mole ratio.

ii. The students chorus the definition of mole and mole ratio

iii. The teacher mentions and shows the students materials used in titration

iv. The students mention the name of materials used in titration

iii. The teacher guides the students in solving some problems on mass-volume relationship

EVALUATION

 The teacher evaluates the lessons by asking the following questions:-

1.       Define mole

2.       List 3 materials used in titration

3.       Calculate the relative molecular mass of 0.4g of oxygen occupied at s.t.p 280cm3

ASSIGNMENT

1.       Calculate the molar mass of Ca(OH)2

2.       Convert 5.3g Na2CO3 to mole

3.       Calculate the following reaction equation: MgO(s) + 2HCl(aq)             MgCl2(aq) + H2O(l). what mass of magnesium oxide is needed to neutralize 25.0cm3 of 0.1 mol dm-3 hydrochloric acid? [O=16.0; Mg= 24.0]. ans=0.050g

  

Comments

Post a Comment

Popular posts from this blog

POST HARVESTING PROCESSES

CHAPTER TWELVES POST HARVESTING PROCESSES 12.1             CONCEPTS AND PHILOSPHY OF POST HARVEST TECHNOLOGY Post-harvest fisheries entails all steps, process and or activities immediately after catch handling and transportation processing and distribution of fish and fishery product where if control is not applied post-harvest losses will occur.         Post –harvest fish losses are a major concern and occur in most fish distribution chains throughout the world. Not only do losses constitute lost income to fishers, processors and traders, they also contribute food insecurity i.e a loss of fish means less fish available for the consumer. POST HARVEST PROCESSES:         Fish are highly perishable. A central concern of fish processing is to prevent fish from deteriorating . Causatic factors of fish spoilage 1. High moisture content.   ...
Read more

NICOM SAT 1

TOPIC: - NICOM-SAT 1    INSTRUCTIONAL MATERIALS: -         Satellite dish REFERENCES BOOK: -     1.      FARINDE O. E e tal, ESSENTIAL PHYSICS FOR SSS, Tonad Publishing Limited. 2.      M. W. ANYAKOHA (2011), NEW SCHOOL PHYSICS FOR SENIOR SECONDARY SCHOOLS, Africana first publishers.    3.      INTERNET PREVIOUS KNOWLEDGE: -     Students have been taught Niger-sat 1 INSTRUCTIONAL OBJECTIVES: - At the end of the lesson students should be able to: - 1.        Explain the concept of NICOM-SAT 1 2.        State the features of NICOM-SAT 1 3.        Uses of NICOM-SAT 1 CONTENT: - NICOM- SAT 1 NigComSat-1 is a Nigerian Communication Satellite. It was launched on 14 may, 2007 in China by China Great Wall Industry...
Read more

FISH SEED PRODUCTION

CHAPTER THIRTEEN FISH SEED PRODUCTION BROOD STOCK SELECTION             Brood stock means a group of sexually mature individuals of a culture species that is kept separate for  breeding purpose. 13.1     DIFFERENCES  BETWEEN MALE  AND FEMALE SEXUALLY MATURED FISHES             Male and female breeders may be easily differentiated by the shape of the body and the relative position of genital papilla. In females, the body is plump and the genital opening is situated above the genital papilla. In males, the body is slender and the genital opening is found behind the genital papilla. External signs of the brood stock A male brood stock will release milt under a slight abdominal pressure: Its belly is not blown up but rather slim; it sometimes has callosities on the head. A female brood stock has a well-rounded and soft  or semi...
Read more