MY CHEMISTRY BLOG.

Sunday, March 22, 2009

♥ Endpoint & Equivalence point

Equivalence point

Defination: The equivalence point, or stoichiometric point, of a chemical reaction occurs during a chemical titration when the amount of titrant added is equivalent, or equal, to the amount of analyte present in the sample.

cases were there are multiple equivalence points, are which multiples of the first equivalent point, such as in the titration of a diprotic acid.

Ways to determine the equivalence point

pH indicator:
This is a substance that changes colour in response to a chemical change. An acid-base indicator (e.g., phenolphthalein) changes colour depending on the pH. Redox indicators are also frequently used. A drop of indicator solution is added to the titration at the start; when the colour changes the endpoint has been reached, this is an approximation of the equivalence point.

Potentiometer:
This is an instrument which measures the electrode potential of the solution. These are used for titrations based on a redox reaction. The potential of the working electrode will suddenly change as the equivalence point is reached.

Conductance:
The conductivity of a solution depends on the ions that are present in it. During many titration, the conductivity changes significantly. For instance, during an acid-base titration, the H+ and OH- ions react to form neutral H2O. This changes the conductivity of the solution. The total conductance of the solution depends also on the other ions present in the solution (such as counter ions). Not all ions contribute equally to the conductivity; this also depends on the mobility of each ion and on the total concentration of ions (ionic strength). Thus, predicting the change in conductivity is harder than measuring it.

Color change:
In some reactions, the solution changes colour without any added indicator. This is often seen in redox titrations, for instance, when the different oxidation states of the product and reactant produce different colours.

Endpoint
The end point (similar, but not the same as the equivalence point) refers to the point at which the indicator changes color in a colorimetric titration.

Credits to http://en.wikipedia.org/wiki/Equivalence_point

♥ Career Choice

My ambition is to become a doctor.

Requirements vary depending on the type of doctor I want to be.

School starts with a four-year bachelor's degree program with strong coursework in the sciences. Then comes another four years in medical school. The college courses you are required to take if you hope to go on to medical school are biology, inorganic and organic chemistry and English. Some medical school programs also require math or calculus and biochemistry. For most schools, you need a grade point average, or GPA, of 3.5 or above. 4.0 is the highest GPA a student may achieve.

Credits to http://education-portal.com/requirements_to_become_a_doctor.html

To study medicine in Singapore, NUS, I would need to ace all my H2 subjects, chemistry, physics and mathematics as well as perform well during the interview. (:

♥ STRENGTHS & WEAKNESS

Strengths
I'm not sure about my strengths in Chemistry yet. I grasp some topics faster while others take me awhile to fully understand them. I'm good at memorizing concepts. However, I would try my best to understand them and ask questions when in doubt. (:

Weakness
I feel that topics that mainly consist calculations like mole and formulas are harder as I teen to mix up the formulas =X

Wednesday, March 4, 2009

♥

SPA tutorial - 3rd March

During chemistry lesson today, we had our first practical lesson! (I love practicals!)
We(combined science students) were thought the to perform titration and the ways to clean the apparatus in order for contamination to not take place(:

After the practical, combined science students(me, jesslyn, keet and a couple more) went for the bridging module to try the experiment. It was really interesting even though I've done it once before during secondary three but that wasn't as successful as yesterday's results. :D

However, the lab teacher(she didn't give us her name =X) pointed out to me that I had a lot of errors in my work):
like the way I read the burette. x.x
or the way I controlled the pipe of the burette.
and tons more! )):

But I think that titration is way more fun than QA! which was really easy =X
and has no challenge =X

I'm more of a hands-on worker haha. xD

Chem lesson later! Can't wait! :D

Tuesday, February 24, 2009

♥

I had my chemistry lesson at O hub today and we went through tutorials using the website Preparatory Chemistry. We did two subtopics from chapter 3 and one subtopic from chapter 4.

Binary Covalent Nomenclature[subtopic of chapter 3]

The three things I've learnt in this chapter:
- I learnt the steps to write the names for binary covalent compounds.

- I have learnt prefixes, Roots of the Nonmetals and the Exceptions .
For example,

`Prefixes:
1 - mon(o)
2 - di
3 - tri

`Roots of the Nonmetals:
S - sulf
Se - selen
F - fluor
Cl - chlor

`Exceptions:
HF can be named hydrogen fluoride or hydrogen monofluoride.

- I have also learnt how to convert names to formulas.