Chemistry Pop-Quiz

Lucas10101

With less than 5 days left, and probably a tough exam ahead, we must really make this thread, to get more chemistry in our head, we must learn more about lead, while tonight going to bed, at 9 o clock getting fed, and our faces getting red, knowing with Chemistry were dead.

Here's one:

Q. What's the name of the yellow precipitate formed when Nitric Acid and Ammonium Molybdate is added to a soluble solution of Phosphate salt in deionised water?

JC 2K3

Ammonia? :S

I hate anion tests....

EDIT: I checked my book and it doesn't say what the yellow precipitate is, guess it's not on the course....

Lucas10101

Close.....Ammonium Phosphomolybdate, it's in my book and I checked that it's also on the syllabus. I'm sure your book has things mine doesn't either. It was also a sample question in a exam papers.

Q. Define (i) Le Chateliers Principal (ii) Hund's Rule (iii) Heat of Combustion?

nedward

LCP If a stress is applied to a system at equilibrium, the system readjusts so as to oppose the stress applied

Hund-If two or more orbitals of equal energy are available, electrins occupy them singly before filling them in pairs.

Heat of combustion of a substance is heat change when one mole of a substance is completely burned in excess oxygen.


You have to heat the PO4 and molybdenum to get a reaction as well.

What is the name of the oil in cloves and give a use for it. When making clove oil, whole cloves are used. Why?

Cipriana

Clove oil? Seems like a trick question, probably has some long fancy name. Whole cloves have more oil than ground cloves. This is also why you pick the cloves before they flower, isn't it? I like this thread, Lucas do you have any other random questions that aren't in the chemistry live book?

Q: When the oxidation reaction between potassium tartrate and hydrogen peroxide is catalysed by cobalt chloride crystals, describe the colour change.

JC 2K3

hmm...

Pink->Green(Intermediate compound)->Pink ?

Cipriana

Well Done *gold star*, ok oxidation no. of oxygen in OF2 (little two)

sully88

+2 because F is the most electronegative element

RafaB

nedward wrote:

LCP If a stress is applied to a system at equilibrium, the system readjusts so as to oppose the stress applied

Hund-If two or more orbitals of equal energy are available, electrins occupy them singly before filling them in pairs.

Heat of combustion of a substance is heat change when one mole of a substance is completely burned in excess oxygen.


You have to heat the PO4 and molybdenum to get a reaction as well.

What is the name of the oil in cloves and give a use for it. When making clove oil, whole cloves are used. Why?

Uegenol. Because ground cloves would char

Lucas10101

It's Eugenol not Uegenol.

Q. In relation to Sigma and Pi Bonds, " A Double Bond is not Twice as Strong as a Single Bond ", Why?

JC 2K3

Because a double bond involves a sigma bond and a pi bond and pi bonds are weaker.

What is the difference between a primary alcohol and a secondary alcohol?

toxick

Lucas10101 wrote:

It's Eugenol not Uegenol.

Q. In relation to Sigma and Pi Bonds, " A Double Bond is not Twice as Strong as a Single Bond ", Why?

because sigma bonds are head on while pi bonds are sideways.

What is the difference between a primary alcohol and a secondary alcohol?

it depends were the OH is in the chain.

edit: forgot question:

Explain how line emission spectra occurs

nedward

toxick wrote:

it depends were the OH is in the chain.

edit: forgot question:

Explain how line emission spectra occurs

A secondary alcohol is an alcohol that has two carbon atoms attached to the -OH functional group.

A line emission spectrum is a series of coloured lines on a dark background formed when light from a gaseous sample of a substance is passed through a prism. Definite lines at definite frequencies are observed corresponding to electron transitions from higher energy levels to lower energy levels.

Electrons in an atom have quantised amounts of energy. When energy is supplied to an atom, electrons become excited and move to a higher energy level. They are unstable here, and fall back down, giving off their energy as a photon of light. Since definite amounts of energy are emitted, by E=ff, definite frequencies are observed.


Give two reasons for the behaviour of carboxylic acids as acids.


By the way, the salt formed (ammonium phosphomolybdate) is on the course. I think you have to know the salts formed in the rest of the anion experiments.

Your Man

nedward wrote:

Give two reasons for the behaviour of carboxylic acids as acids.

Solube in water: due to H bonding which occurs twice, i.e two water molecules form two H bonds with one molecule of carboxylic acid.
High Boiling Points: carboxyclic acids form dimers which give them extra stability.

How are impurities removed during the production of ethyne?

lemansky

Your Man wrote:

How are impurities removed during the production of ethyne?

By bubbling it through acidified copper sulfate solution.

Relative atomic mass is defined as.......

JC 2K3

The average mass of an atom of an element depending on the abundance of different isotopes of that element in a particular environment.

Write the electronic configuration of Chromium.

lemansky

JC 2K3 wrote:

Write the electronic configuration of Chromium.

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5


Why is this the case, and not 4s2, 3d4?

toxick

lemansky wrote:

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5


Why is this the case, and not 4s2, 3d4?

due to 3d5 is more stable as it is a half filled sub-level. it is the forming of the octet rule, were electrons try and fill the outer must lair with eight electorns.

State two properties of transition metals.

JC 2K3

Because it makes the 3d orbital, half full, which is a particularly stable configuration.

Define Eutropification.

Lucas10101

Edit: Eutrophication is the enrichment of water with nutrients depriving it of oxygen leading to the excessive growth of algae.

Q. When titrating Nitric Acid against Sodium Hydroxide, What pH range is necessary and what suitable indicator could be used in this titration that complement both the indicator and pH? Give reasons for your answer and provide an example of an unsuitable indicator if any for this reaction explaining why?

bebop!

Transition Elements

1. Exhibit Variable Valency
2. Form coloured compouds
3. Can behave as catalysts

Eutrophication is the over-enrichment of water with nutrients such as nitrates and phophates.

Define B.O.D!

toxick

Eutrophication is the enrichment of water with nutrients, which leads to excessive growth of algae


State two properties of transition metals.

toxick

B.O.D is a test to measure the demand that water has for dissolved oxygrn.

dont know lucas question so gonna say it again :P

Q. When titrating Nitric Acid against Sodium Hydroxide, What pH range is necessary and what suitable indicator could be used in this titration that complement both the indicator and pH? Give reasons for your answer and provide an example of an unsuitable indicator if any for this reaction explaining why?

Lucas10101

It's a Strong Acid against a Strong Base I think and that means a suitable indicator would be Methyl Orange, Litmus or Phenolphthalein. The pH range for these is between 3-10 between a strong acid/strong base titration. There is no unsuitable indicator as it covers the range 3-10.

Explain the Inductive Effect of Carboxylic Acids?

Cipriana

Quick question is methanal triangular planar?

Thomas_S_Hunterson

toxick wrote:

State two properties of transition metals.

*Exhibit Variable valency
*Form Different coloured salts
*Often good catalysts
*They display a variety of oxidation states

Cipriana wrote:

Quick question is methanal triangular planar?

No, I don't think it's shape is on the course
It's something like this:

Note the double bond

madnirvana

Q- difference between Ethanal and Ethanoic acid.

how to prepare ethanoic acid from ethanal ?;)

nedward

BOD is the amount of dissolved oxygen consumed by biological demand when a sample of water is kept at 20C, in the dark, for five days.

The inductive effect is one of the main reasons for the behaviour of carboxylic acids as acids. The electronegative O atom double-bonded to the C attracts its electrons, leaving it with a delta + charge. This attracts electrons from the O of the -OH group, and in turns draws away the electron of the H, leaving it with a slightly positive charge.

Name the two elements that Mendeleev predicted the existence of and give one example of two elements whose order he reversed to make them fit into his Periodic Table.

bebop!

Mendeleev predicted germanium and gallium

He wrongly reversed Tellurium and Iodine.

Q1. What is an ideal gas?

Q.2 In reality no such gas exsists. Explain an assumption of the Kinetic Theory which is not strictly correct under all conditions.

adamcp

1.an ideal gas is one which obeys all assumptions of the kinetic theory under all conditions of temperature and pressure

2.one of it's assumptions is a gas' forces are elastic i.e. if a molecule hits the wall of a container it will bounce back with the same force

Q can't think of much so.........what is the Paschen series?

JC 2K3

A series of light in the infra-red spectrum?