Most Difficult Chem Definitions?

jaydigity

So, what do you think they are?Was thinking we could use this as last minute revision aid

Hess' Law If a chemical reaction takes place in a number of stages, the sum of the heat changes in the separate stages is equal to the change if the reaction were carried out in one step

Gay-Lussac's law of combining volumes In a reaction between gases, the volumes of the reacting gases and the volumes of any gaseous products are in the ratio of small whole numbers, provided the volumes are measured at the same temperature and pressure

...Gay-Lussac and Hess both talk a lot of shít :rolleyes:

theliam

define burette

Your Man

has to be the one for chromatography

JC 2K3

jaydigity wrote:

So, what do you think they are?Was thinking we could use this as last minute revision aid

Hess' Law If a chemical reaction takes place in a number of stages, the sum of the heat changes in the separate stages is equal to the change if the reaction were carried out in one step

Gay-Lussac's law of combining volumes In a reaction between gases, the volumes of the reacting gases and the volumes of any gaseous products are in the ratio of small whole numbers, provided the volumes are measured at the same temperature and pressure

...Gay-Lussac and Hess both talk a lot of shít :rolleyes:

Well, if you learn them word for word I guess....

If you're smart about it you'll just actually learn what thay mean.

For example, Gay Lussac's Law is just:
If A + B -> C and A, B and C are gasses
And X, Y and Z are their volumes at a constant T and P
Then X : Y : Z is a simple whole number ratio.

Lucas10101

Chromatography is a separation technique where the mobile phase moves in contact with a selectively adsorbant stationary phase.

Heat of Reaction is the heat change when the number of moles of reactants indicated in the balanced equation for the reaction react completely.

The Rate of Reaction is the change in concentration per unit time of any one reactant or product,

The Molarity of a solution is the number of moles of solute per litre of solution.

The Empirical Formula of a Compound is the formula which gives the simplest whole ratio of elements in a compound.

Electronegativity is the relative attraction that atoms have for the shared pair of electrons in a covalent bond.

Relative Atomic Mass is defined as the average of the mass numbers of the isotopes of the element, as they occur naturally, taking their abundances into account and measured with 1/12 the mass of Carbon 12 isotope.

And the hardest definition.....:)

Eutrophication is the enrichment of water with nutrients leading to the excessive growth of Algae.

madgal

1. Relative Atomic Mass is the average of the mass numbers of the isotopes of the element as they occur naturally taking their abundancies into account and compared with 1/12th of the mass of the carbon-12 isotopes.

2. Isotopes are atoms of the same elements that have different mass numbers due to the different numbers of neutrons in the nucleus.

3. The Aufbau Principle states when building up the electronic configuration of an atom in its ground state, the electrons occupy the lowest available energy level.

4. Pauli Exclusion Principle states that no more than 2 electrons can occupy an orbital and they must have opposite spin.

5. Hund's Rule states that when two or more orbitals of equal energy are available, electrons occupy them singly before filling them in pairs.

Lucas10101

1. Le Chateliers Principal : If a stess is applied to a system at equilibrium, the system readjusts itself to relieve the stress applied.

2. Energy Level: A fixed amound of energy an atom in an element may have.

3. Oxidation Number: is the charge that an atom has or appears to have when electrons are distributed according to certain rules.

4. Bond Energy is the energy required to break one mole of covalent bonds and to separate the neutral atoms completely from each other.

5. Electrochemical Series: A list of elements in order of their standard electrode potentials.

jaydigity

JC 2K3 wrote:

Well, if you learn them word for word I guess....

If you're smart about it you'll just actually learn what thay mean.

For example, Gay Lussac's Law is just:
If A + B -> C and A, B and C are gasses
And X, Y and Z are their volumes at a constant T and P
Then X : Y : Z is a simple whole number ratio.

hmmm, true, far easier to learn, but sometimes, if you understand a concept and define it in your own words, you miss out on vital terms etc. The chem marking scheme is VERY particular on this too, so.... I think I'll just have to learn mindless drivel

Lucas10101

Speaking of Chemistry Marking Schemes being particular, one year when flame tests were being examined and the question as to what colour Potassium burns at......Purple?.....No......They only strictly accepted Lilac.

Another strict one, or silly one was in the Mandatory Experiment where Hydrogen Peroxide gets Catalysed by Manganese Dioxide, when you had to draw the diagram, you had to put the Mn02 in a test tube inside the hydrogen peroxide flask or else you lose marks. The textbook though shows the Mn02 in the flask mixed with Peroxide, just shows how particular or strict answering that you have to guess to be right nearly as in this example.

Splicer

Lucas10101 wrote:

Speaking of Chemistry Marking Schemes being particular, one year when flame tests were being examined and the question as to what colour Potassium burns at......Purple?.....No......They only strictly accepted Lilac.

Another strict one, or silly one was in the Mandatory Experiment where Hydrogen Peroxide gets Catalysed by Manganese Dioxide, when you had to draw the diagram, you had to put the Mn02 in a test tube inside the hydrogen peroxide flask or else you lose marks. The textbook though shows the Mn02 in the flask mixed with Peroxide, just shows how particular or strict answering that you have to guess to be right nearly as in this example.

as in an actual testtube dipping into H2O2 solution??? u sure?

Lucas10101

Yes, it was on the Marking Scheme, it's also in Rapid Revision Page 110. Although, the problem is, what can we do, if we draw it that way this time and they don't accept it, not really fair for students.

jaydigity

Lucas10101 wrote:

Speaking of Chemistry Marking Schemes being particular, one year when flame tests were being examined and the question as to what colour Potassium burns at......Purple?.....No......They only strictly accepted Lilac.

Another strict one, or silly one was in the Mandatory Experiment where Hydrogen Peroxide gets Catalysed by Manganese Dioxide, when you had to draw the diagram, you had to put the Mn02 in a test tube inside the hydrogen peroxide flask or else you lose marks. The textbook though shows the Mn02 in the flask mixed with Peroxide, just shows how particular or strict answering that you have to guess to be right nearly as in this example.

The worst I've ever seen (and I can't remember where this wass, it may have been a pre paper), was whereby marks were deducted if you didn't draw a plug on your hotplate :mad: !!!!!!!

JC 2K3

Lucas10101 wrote:

Another strict one, or silly one was in the Mandatory Experiment where Hydrogen Peroxide gets Catalysed by Manganese Dioxide, when you had to draw the diagram, you had to put the Mn02 in a test tube inside the hydrogen peroxide flask or else you lose marks. The textbook though shows the Mn02 in the flask mixed with Peroxide, just shows how particular or strict answering that you have to guess to be right nearly as in this example.

My book shows the MnO2 in a test tube.....

Lucas10101

Well, it's sort of unfair that they should give marks for one textbooks way over the other and vice-versa in every year.

JC 2K3

Yup.

Has anyone noticed that those who set the exams(and I mean every exam) don't seem to be very in touch with how the courses are taught, what is being taught and in some cases, what is on the syllabus(I'm looking at you, Physics)?

lemansky

JC 2K3 wrote:

Yup.

Has anyone noticed that those who set the exams(and I mean every exam) don't seem to be very in touch with how the courses are taught, what is being taught and in some cases, what is on the syllabus(I'm looking at you, Physics)?

Pretty much.The people who actually set the papers aren't active teachers and my god does it show.

Lucas10101

This is supposed to be for Chemistry definitions so I have one more:

Define ".....Oh **** This"