Hello,been long since i last updated.Shall give some brief happenings for Chemistry:
#1:Promotional Examinations (1) H2 CHEMISTRY is really badly done in my perspective,excluding the "Overall Results".
#2:Chemistry topics are getting tougher,can sense it.
#3:Shall update about the term ,"Standardization" in this post,since Ms.Gee asked us to do some research for those who are not too clear about the definition.

-Standardization of a solution refers to an experiment in which the concentration of a solution is determined.
-A process in which the value of a potential standard is fixed by a measurement made with respect to a standard whose value is known.

Can't seemed to find any useful definitions!!!!!!!!!!!!

Shall talk about Ideal Gas.
Ideal Gas equation: pV=nRT
p-pressure in Pa
V-volume in m^3
n-amount in mol
R-universal gas constant (8.314)
T-temperature in K

According to the Kinetic Particle theory of gasses, an ideal gas will have:

-Volume of gas particles negligible as compared to volume of the container
-Negligible intermolecular forces between gas particles
-Gas particles are moving in constant random motion
-Gas particles collides in an perfect elastic motion

Shall talk about Energetics:
So far,we had only learnt the various definitions of different types of enthalpy change/energy.For example,Standard enthalpy change of solution,Standard enthalpy change of hydration,Standard enthalpy change of neutralisation,Standard enthalpy change of atomisation,Standard enthalpy change of reaction,Standard enthalpy change of formation,Bond dissociation energy,Lattice energy,Electrons Affinity,etc.Just remember that the standard conditions is 1atm pressure,298K in temperature.

Finally to summarise(with questions!)
Why is enthalpy change for exothermic reactions negative?
Because energy has been released to the surroundings. The products therefore have a lower enthalpy than the reactants and the final enthalpy is less than the initial enthalpy

Why is standard enthalpy changes of combustion always negative?
Because heat is always evolved, the reaction is exothermic and therefore heat is lost to the surroundings. The energy required to break bonds is always less than the energy released when bonds are formed

Alright,see ya guys! :-)
P.s:I am just plain happy and blessed recently,excluding those physical and mental pain.

Hello teachers,i want to know if it's still necessary to keep this "Chemistry Blog" and if yes,do we still need to keep the updates going on?Thankyou!

What are the properties of ethanedioic acid that make you think that it is a good choice for standardisation of alkali(NaOH)?(Why we do not use HCl or H2SO4 to standardise)

Is it because that it is,
:a weak acid,pure,stable in air, readily soluble in water and have a relatively large relative formula mass.

:a solid acid whose mass is an accurate measure of the number of moles of H+ ions it will require.

Anyway for extras:
:We cannot prepare standard NaOH solution by dissolving a measured mass of pure NaOH in a known volume of water,because NaOH is
hygroscopic,which means it readily absorbs atmospheric moisture. (Results in inaccurate concentration?)

:The balanced equation for the acid-base reaction involved in the standardization procedure is;
H2C2O4(aq) + 2 NaOH(aq) → Na2C2O4(aq) + 2 H2O(l)

Ethanedioic acid.



Molecular formula : C2H2O4 /C2H2O4 .2H2O (?)
MW : 90.04
CAS No. :144-62-7


Nature transparent colorless crystals or a white powder, odorless, The findings. 1.650g/cm3 density. 101 ° C melting point. The boiling point of 150 ° C (sublimation). Slightly soluble in water, soluble in water, alcohol, ether-soluble, non-soluble in benzene. In dry air heating or small crystal water will be lost. The organic acids are strong acid, alkali and the Sino-and role. With reductive. With sulfuric acid role lose moisture, the foundation decomposed into dioxide and carbon monoxide. And the role of oxidant easily oxidized into carbon dioxide and water. Toxic to the skin, mucous membrane and stimulate corrosion vulnerable by the epidermis, mucosal absorption cause poisoning. Air maximum allowable concentration of 1m g/m3.

My goodness.It's really suffocating and tedious for me since I have no background of whatsoever the "orbital" thing is about in the new topic,Atomic Structure.
First of all,i was lucky because i had my sister's notes(which was a miracle she didn't threw it yet),which aided a lot on my study for this topic.Secondly,i really don't understand anything when Mr Tan explained roughly on the topic to the class (So sorry!) It's my fault,haven't been reading up
So,apparently,chemistry's taking a hell lot of my sleeping time.haha.

Back to the main reason for this post,..

Protons(p) is positioned in nucleus,with +1electric charge,relative mass of 1.
Neutron(n) is positioned in the nucleus,with 0
electric charge,relative mass of 1.
Electron(e^-) is positioned around the nucleus,with -1 electric charge,relative mass of 1/1840.


Principal quantum numbers >No of energy lvl>e.g (n=1,n=2....)
Types of subshells: s,p,d,f. (Mr tan said we only need to learn up to s,p,d)
The sequence goes, 1s^2,2s^2,2p^6,3s^2,3p^6,3d^10
When drawn in boxes,(electron-in-boxes method).................each box can draw up to 2 electrons.
By which their spins is always opposite,starting from up arrows,followed by downward arrows
1s have the lowest energy,4f-the highest,however to take note,3d has higher energy than 4s

shapes of orbitals for s,-spherical
shapes of orbitals for p(px,pz,py)-Dumb-bell
Different aces of symmetry,mutually,perpendicular to one another,orbitals (px,py,pz) with the same p.q.n have the same energy,ie.they are degenerate

the laws/rules to follow:
1)Pauli Exclusion Principle
2)Aufbau (for building up) Principle
3)Hund's Rule

Ok,i typed this all out because i find the online notes gave quite a lot redundant information.(ops) haha.It's quite messy though,sorry Ms Jee/Mr Tan

As for Ionisation Energies,NEXT TIME PLEASE!

Question:How does the equivalence point of a titration differ from its end point?

Answer:
The equivalence point is the point where the number of moles of base equal the number of moles of acid. The end point is the point where the indicator being used changes color. If the indicator is chosen correctly, the end point will essentially be exactly at the equivalence point. The point of the titration is to find the equivalence point -- the end point is just a very close approximation to it. This is because the pH of the solution changes very rapidly close to the equivalence point. Therefore, the indicator will change colour very close to the equivalence point because of the steepness of the pH change.

I understood now,clearly!
C:
C:
C:

Ohhhh..I've just realised my dates and time's so screwed up.
And it's cool,because that meant that i woke up on 4.12a.m(previous post) just to post an entry.
Now now,how hardworking am i?HAHA