Characteristics of sp, sp2, sp3- hybrid orbitals

Characteristics of sp-hybrid orbital

·         Results from mixing of one s and one p-orbital.

·         Equivalent and symmetrical.

·         All orbitals have the same shape and energy.

·         Shape is oval shape which is in between spherical and pear shape.

·         Sp- hybrid orbitals are collinear. That means they are aligned in a straight line in opposite direction.

Characteristics of sp²-hybrid orbital

·         Results from mixing of one s-orbital and two p-orbitals.

·         They have the same shape and energy.

·         Lie in one plane.

·         Shape tends more towards the pear shape as the contribution of p-orbital is greater than the contribution of s orbital.

·         Spatial arrangement is trigonal. Angle between each pair is 120^o

Characteristics of sp³- hybrid orbital

·         Results from combination of one s-orbital and three p-orbitals.

·         Orbitals are equivalent and symmetrical.

·         Same shape and energy.

·         Arranged in tetrahedral angle where the angle between each pair is 109.5^o

·         Pear shaped but the lobes are much spread and somewhat shorter in length than the original p-orbitals.

Preparation of Sodium Carbonate extract - Identify Sulfates, Nitrites, Nitrates and Phosphates by using the prepared Sodium carbonate solution

Preparation of Sodium Carbonate extract

200mg of the unknown sample, 1g of Na₂CO₃ and 50ml of distilled water was added into a clean dry flask later boiled using a tripod stand. This was done by clamping a funnel above the flask to reduce evaporation.

It was boiled for about 5 minutes.

Afterwards solution was cooled and filtered using a filter paper.

A colorless filtrate was obtained.

Identify Sulfates, Nitrites, Nitrates and Phosphates by using the prepared Sodium carbonate solution

SO₄^2-

Procedure	Observation
5 drops of Na2CO3 extract was acidified with dil. HCl in boiling tube. Acidity was checked with litmus. It was kept in a hot water bath for about 3 minutes and added 3 drops of BaCl2	When the extract was acidified with HCl, it turned into brownish red colour. White colour precipitate was formed.

NO₂^-

Procedure	Observation
1ml of Na2CO3 extract was heated with dil. H2SO4 in boiling tube. The evolved gas was checked with starch.iodide paper.	With H2SO4 the extract turned into reddish brown colour. Brown fume was evolved when heating. It turned the starch-iodide paper into blue colour.

NO₃^-

Procedure	Observation
1ml of Na2CO3 extract was heated with 100mg Sulphamic acid in a boiling tube. Later dil.NaOH was added and heated until the evolution of NH3 is ceased. It was again checked with Devarda’s alloy.	In the presence of Sulphamic acid the solution turned into brownish red. Pungent smelling brownish colour gas was formed and the it continued for awhile in Devarda’s alloy.

PO₄^3-

Procedure	Observation
1ml of Na2CO3 extract, 1ml of dil. HNO3 and 10ml ammonium molybdate was heated gently in a boiling tube.	With HNO3 the extract turned into brownish red colour. Later a yellow colour precipitate was obtained.

What’s the purpose of preparing Na₂CO₃ extract?

It gives an expedient way of bringing all the anions of the sample into solution. Otherwise they might be insoluble and couldn’t carry out the experiment properly. Also it prevents the cation in interfering.

What is the importance of Na₂CO₃ extract to be clear and colourless?

This provides a better setting to observe formations of precipitates, colour changes which take place during the experiment.

Is the Na₂CO₃ extract basic or acidic?

It is slightly basic.

Went's experiment- Stem curvature test

Theory

Increment of the stem occurs due to the concentration of the Auxin produced at the apical region.

Therefore;

1.      Increment of the length ∝ Concentration of Auxin      1

As the tips of the shoots are placed on the Agar surface where the Auxin is available,

2.      Number of tips ∝ Concentration of Auxin

From equation 1 and 2;

Increment of the length ∝ Number of tips

This is used to plot the graph.

Procedure

The apices of the provided Vigna sinensis plant stems were cut off using a razor blade.

Each of them was placed erect on the agar surface which allows equal distribution of Auxin among them in the Petri dish.

-Tips placed on the Agar surface in the petri dish-

 Groups should be formed and each of it should place 10, 20, 30, 40, 50 or 60 tips on theirs Petri dishes.

Dishes were incubated for 20 hours.

Tips were removed from the Petri dishes and dishes were transferred into the refrigerator.

After two days the apices of the provided Vigna sinensis plants grown in pots were removed with a blade.

Initial height of the decapitated stems was measured.

Small cubes about 2×2 mm² of agar from the dishes where the tips had been placed were taken off.

They were placed symmetrically on the decapitated stems.

A control was also setup with an untreated agar block of the same size.

Plants were observed again after 72hours and measured the height of the plants.

What is the effect of replacing the shoot tip with treated agar?

It would provide homogenous concentration of Auxin to all the test plants. Also it would be easy to carry out with control plant, without treating the agar with Auxin.

What were the practical difficulties you faced in this experiment?

Apices of the provided plants are very small. Therefore it had to be removed very carefully.

Diameter of the plant is also very small. Therefore placing the agar block on the decapitated plant was difficult.

Comparative anatomy of the skulls of primates

Loris- Loris spp

• As the brain is small, brain case is smaller than the other primates.
• Well developed supra orbital crest is present.
• Post orbital bar is also completed.
• Tympanic bulla is reduced.
• Comparatively short face.
• Eyes are forwardly directed and large.
• All teeth are pointed.
• Incisors in upper jaw are small.
• Dental formula:- 2/2, 1/1, 3/3, 3/3

Gorilla- Gorilla gorilla

• Brain case is quite smaller comparing to the whole skull.
• Low brain capacity comparative to the other Anthropoides.
• Flat supra occipital bone.
• Supra orbital bone is prominent.
• Supra occipital, supra orbital and temporal crest are well developed for a strong muscle attachment.
• Gorilla is a carnivore animal. Therefore the canines are much elongated and sharp.
• Males have larger canines than the female.
• Dental arch is rectangular.
• Dental formula is 2/2, 1/1, 2/2, 3/3

Orang Utang- Pongo spp

• Brain case is smaller comparative to the whole skull.
• Rounded supra occipital bone.
• Supra orbital ridges are not much prominent as in gorilla.
• Supra occipital and temporal crests are well developed.
• Males have large canines.
• Molars are bilophodont.
• Dental formula:- 2/2, 1/1,2/2,3/3

Chimpanzee- Pan troglodyteq

• Brain case is not smaller comparing to the whole skull.
• Therefore the brain capacity is high.
• Skull surface is smooth and rounded.
• Supra occipital and temporal crests are absent.
• Snout is comparatively long.
• Dental arch is U shaped.
• Males have large canines.
• Dental formula:- 2/2, 1/1, 2/2, 3/3

Human- Homo sapiens sapiens

• Highest brain capacity is shown.
• Smooth and rounded skull.
• Chin is present.
• Flat facial area.
• Supra orbital ridges are much reduced.
• Deeply downward foramen magnum.
• Dental arch is U shaped.
• Canines are small.
• Dental formula:- 2/2, 1/1, 2/2, 3/3