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Standardization of Sodium Hydroxide with Hydrochloric Acid

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Determine the normality of the given sodium hydroxide solution using standard hydrochloric acid solution containing 3.6 gL-1


The determination of the normality of sodium hydroxide is based on the reaction between sodium hydroxide and hydrochloric acid as follows:

HCl + NaOH --> NaCl + H2O

From the equation it is clear that one mole of hydrochloric acid (one equivalent) requires one mole of sodium hydroxide for complete neutralisation. Therefore, the equivalent mass of sodium hydroxide is same as its molecular mass (40).

Eq. mass of HCl = M.Mass = 36.5

Eq. mass of NaOH = M.Mass = 40

A known volume of sodium hydroxide is titrated against the standard hydrochloric acid using phenolphthalein as indicator. Knowing the volume and the normality of the acid, the normality and the mass per litre of sodium hydroxide are calculated.


End Point

In burette

In pipette


Pink to colourless

HCl solution

NaOH solution



A clean burette is rinsed with the standard hydrochloric acid solution. The burette is then filled with the solution, the stop cock is opened and the nozzle of the burette also is filled with the acid. After the air bubbles have escaped, the level of the acid is brought to the zero mark and the reading is noted. It is then clamped to a stand.

A pipette is rinsed with the sodium hydroxide solution. 20mL. of this solution is pipetted out into a clean conical flask. One or two drops of phenolphthalein are added to it. The conical flask is placed on a white porcelain tile below the burette. The level of nozzle tip of the burette should be inside the flask. It is then titrated against hydrochloric acid taken in the burette.

The acid is run into the sodium hydroxide solution in small quantities by regulating the stop-cock with the left hand. Mean while the flask is gently shaken with the right hand. The liquid in the conical flask is given a swirling motion. About one mL of the acid is added each time with shaking upto about 15 mL and then 0.5 mL each at a time till the colour of the solution fades. At this stage the sides of the conical flask are washed with small quantities of water using a wash bottle. There after the acid is added in drops. The titration is continued till the pink colour just disappears with a last single drop of acid. This is the end point. The final reading is noted. The difference between the final and initial readings gives the volume of acid added. The titration is repeated till concordant values are obtained. The titre values are tabulated as shown below. From the titre value, the normality and the mass per litre of sodium hydroxide are calculated.

NaOH x HCl

Expt. No.

Volume of NaOH

Burette reading

Volume of HCl














Volume of NaOH solution, V1 = 20 mL

Let normality of NaOH solution = N1

Normality of HCl, N2 = Mass per litre/Eq. Mass = 3.6/36.5

Let volume of HCl = V2 mL

N1 x V1 = N2 x V2

Therefore, Normality of NaOH, N1 = (V2 X N2)/V1

Therefore, Mass per litre of NaOH = Normality x Eq.mass = N1 x 40


Normality of NaOH solution = ………..

Mass per litre of NaOH solution = ………g

Temperature Dependence of Electric Resistance

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Investigatory Project on Temperature Dependence of Electric Resistance

Aim: To investigate the dependence of the electric resistance of different materials (conductors and semiconductors) on different temperatures.

Apparatus: Metre bridge, A coil of copper wire (resistance about 10Ω), A semiconductor material (a carbon resistor of about 10Ω), A cell, Resistance box, Galvanometer etc.

Theory: The electrical resistance of a conductor is found to increase with increase of temperature (positive temperature coefficient of resistance), while that of a semiconductor decreases with increase of temperature (negative temperature coefficient of resistance).

Using metre bridge, the unknown resistance is calculated to be X = Rl/(100-l)

where R — Known resistance

l — Balancing length


i. Conductor: The coil of copper wire of about 10Ω resistance is placed inside a test tube containing liquid paraffin. The ends of the coil are connected to the tell gap of the metre bridge and the electrical connections are made as shown in the figure. Adjusting the position of jockey, the balancing point is determined. It is measured as 'l'. The temperature of the coil is noted using a thermometer. Similar way, balancing point is determined for different temperature (say 30, 50, 70, 90) by heating the liquid paraffin. A graph is plotted with temperature t along the X-axis and resistance X along the Y-axis. It is found to be a straight line with positive slope.

ii. Semiconductor: The experiment is performed with a given semiconductor, the resistance is determined for different temperatures. A graph is drawn with temperature t along the X-axis and resistance of semiconductor X along the Y-axis. It is found to be a straight line with negative slope.

Observations and Calculations

emf of the cell = …….. V

Range of resistance of box = 0 to ………

Range of thermometer scale = …… to ……

Trail No:


Temperature (t)

Known resistance (R)

Balancing length (l)

(100 - l)

Resistance, X = Rl/(100-l)






















Semi conductor






Temperature Resistance Graph


The resistance of both the conductor and the semiconductor are affected by the temperature changes.

i. Resistance of the conductor increases with increase of temperature.

ii Resistance of the semiconductor decreases with increase of temperature.

Zoology Viva Questions and Answers

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Zoology Practical Viva Questions and Answers

Investigatory Project on Setting up and Maintenance of an Aquarium

1. What is an aquarium?

Aquarium is an open rectangular glass tank providing a condition similar to pond for the growth of fishes and water plants.

2. Name two ornamental fishes?

Gold Fish (Carassius auratus) and Guppy (Poecilia reticulata)

3. Name two water plants used in an aquarium?

Hydrilla and Valisnaria

Investigatory Project on Some insect pests and their control

4. What are pests?

Pests are organisms which destroy and damage crops and food grains during various stages of cultivation and storage.

5. Name any two paddy pests.

Leptocoriza acuta and Tryporyza incertulas.

6. Name a pest that attacks coconut palm.

Oryctes rhinoceros

Investigatory Project on Prepare an account of wild animals after visiting a Zoo or National Park

7. What is wildlife? Give example.

The uncultivated species of plants and animals living in their natural habitat is known as wild-life.

8. Give the scientific names of lion and elephant.

Panthera leo and Elephas maximus

9. What is Project Tiger?

It is a scheme to protect tigers from extinction. It was launched by the Govt. of India in 1973.

Investigatory Project on Control of Mosquitoes

10. Name the different species of mosquitoes found in your locality.

Anopheles, Culex and Aedes mosquitoes

11. Name two larvivorous fishes.

Gambusia and Aplocheilus

12. Name the diseases spread by Culex, Anopheles and Aedes

Culex – Elephantiasis

Anopheles – Malaria

Aedes – Dengue fever

Investigatory Project on Preparation of a report with illustration and photos from newspapers and magazines dealing with pollution

13. What is pollution?

Undesirable change in the physical, chemical and biological characteristic of air, water and land that may harmfully affect the living beings including man is called pollution.

14. What are pollutants?

The agents that cause pollution are known as pollutants.

15. Name any three air pollutants?

Carbon monoxide, Sulphur dioxide and Hydrocarbons

16. Distinguish between degradable and non degradable pollutants?

Pollutants which are degraded by microbial action and radiation are called degradable pollutants.

Eg: Domestic Sewage

The pollutants which are not degraded are known as non-degradable pollutants.


Investigatory Project on DNA Model

17. What is DNA?

DNA or Deoxyribo Nucleic Acid is the genetic material in all organisms except certain viruses.

18. Who proposed the double helix model of DNA?

Watson and Crick (1953)

19. Name the nitrogen bases found in DNA.

Adenine, guanine, cytosine and thymine

20. Expand DNA

Deoxyribo Nucleic Acid

21. Which is the functional unit of DNA?


Investigatory Project on Survey of Human Phenotypic Characters

22. What is phenotype?

The visible characters of an organism are known as phenotypic characters.

23. What is genotype?

The genetic constitution of an organism is known as genotype.

24. What do you mean by hereditary characters?

The characters which transmit from parents to offspring are known as hereditary characters.

25. Name any two phenotypic characters that are heritable.

Fused ear lobes and rolling of tongue.

Investigatory Project on Preparation of Vermi Compost using household wastes, market wastes etc.

26. What is vermin compost?

It is the excretory product of earthworm rich in nutrients and minerals.

27. Name the elements found in vermin compost.

Nitrogen, potassium, and phosphorus

28. Mention the merits of vermin compost.

Vermi compost is safe, economic and ecofriendly.

Investigatory Project on Preparation of Rectal Ciliates in Amphibians

29. Name any two ciliates found in the rectum of frog.

Opalina and balantidium

30. What are ciliates?

Ciliates are unicellular animals. They possess cilia. They belong to the phylum protozoa.

Investigatory Project on Study on the Bird Fauna in the Locality

31. What is Ornithology?

Study of birds is known as ornithology

32. Who is called Bird Man of India?

Dr. Salim Ali

33. Name two birds found in your locality.

Crow and Bulbul