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?

Shox

Paschen series, is dat on the course??

JC 2K3

Yes.

What does edta stand for?

alancork

ethylene diamine tetra-acetic acid..

Q. What's the difference between the Greenhouse Effect and the Enhanced Greenhouse Effect ( thats on the option...)

Your Man

ethylene diamine tetracetic acid? or somthing like that.

Describe how iron tablets are made into solution in the iron tablet experiment and give a reason as to why they are dissolved in H2SO4?

madnirvana

ethelenediamenetetraacetic acid

madnirvana

Your Man wrote:

ethylene diamine tetracetic acid? or somthing like that.

Describe how iron tablets are made into solution in the iron tablet experiment and give a reason as to why they are dissolved in H2SO4?

crush the tablets with mortar and pestle, Add few drops of H2So4

it adds H+ ions. prevents hydrolosys

JC 2K3

alancork wrote:

ethylene diamine tetra-acetic acid..

Q. What's the difference between the Greenhouse Effect and the Enhanced Greenhouse Effect ( thats on the option...)

You pay extra for the latter.

(I dunno, I don't do the option )

nedward

alancork wrote:

ethylene diamine tetra-acetic acid..

Q. What's the difference between the Greenhouse Effect and the Enhanced Greenhouse Effect ( thats on the option...)

The greenhouse effect is the trapping of the Sun's heat in the atmosphere.

The enhanced effect is the more than usual heat being trapped due to increased amounts of greenhouse gases in the air because of human activities.


How would you go about converting ethanoic acid to ethanal, and thence to ethanol?

Lucas10101

Reflux & Distillation for the forward one Ethanol, Ethanal and Ethanoic Acid.
Not sure about the reversed one.

Q. What's the difference between the Haber and Contact Process and under what conditions do each normally suffice at and what's formed in each process?

Your Man

Haber process is the manufacture of ammonia, ideal conditions are high pressure and low temperature but a temp of 200 atmospheres is used as HP is too costly, a high temp is used to bring the reaction to equilibruim faster.
Contact Process: the industrial production of sulphuric acid, high pressure is ideal but too costly, also a low temp is ideal but a temp of 450 degrees is used.

Distinguish between intramolecular bonding and intermolecular bonding.

JC 2K3

Intramolecular - Bonding between atoms in molecules.
Intermolecular - Bonding between molecules in substances.

Lucas10101

Distinguish between:

(i) Van Der Waals Forces
(ii) Dipole-Dipole Forces
(iii) Hydrogen Bonding

What is a dipole, how do these affect Boiling Points, if at all?

Shox

Van der waals forces: only between non polar molecules

Dipole dipole forces : Only between polar molecules

Hydrogen bonding: Type of dipole dipole force, when a hydrogen atom is bonded to a small electronegative atom of oxygen, fluorine or nitrogen


A 25cm(cubed) sample of a 2M hydrochloric acid solution is diluted to 2 lites with water. Calculate the concentration of the resulting solution?
(took this from the papers, my stoichiometry sucks)???

madnirvana

Shox wrote:

Van der waals forces: only between non polar molecules

Dipole dipole forces : Only between polar molecules

Hydrogen bonding: Type of dipole dipole force, when a hydrogen atom is bonded to a small electronegative atom of oxygen, fluorine or nitrogen


A 25cm(cubed) sample of a 2M hydrochloric acid solution is diluted to 2 lites with water. Calculate the concentration of the resulting solution?
(took this from the papers, my stoichiometry sucks)???

im not studying stoichiometry ATALL its the worst chap..:mad:


diference between ethanal and ethanoic acid?

JC 2K3

Shox wrote:

A 25cm(cubed) sample of a 2M hydrochloric acid solution is diluted to 2 lites with water. Calculate the concentration of the resulting solution?
(took this from the papers, my stoichiometry sucks)???

Lol, stoichiometry's píss, in this instance, volume is indirectly proportional to molarity.

2000/25 = 80
2/80 = 1/40 = 0.0025M

Simple

madnirvana wrote:

diference between ethanal and ethanoic acid?

Ethanal = CH3CHO
Ethanoic Acid = CH3COOH

So that means Ethanal is a methyl group bonded to a carbonyl group and Ethanoic Acid is a methyl group bonded to a carboxyl group, right?

What is the Electrochemical Series?

genericgoon

A series which arranges metals in terms of their reactivity

Expalin the electron pair repulsion theory.

bebop!

Valence Shell Electron Pair Repulsion Theory. (VSEPR)

This theory states that the shape of a molecule depends on the number of pairs of electrons in the outer shell of the atom.

The pair of electrons that are not involved in a covalent bond are called a lone pair. The total number of electron pairs around the atom of the molecule determines the shape of the molecule, since elctrons are negatively charged, pairs of electrons will repel each other and arrange themselves so that are as far apart as possible from each other.

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Q. In the experiment to produce ethyne gas, Liquid X is dropped onto solid Y to produce ethyne gas.

Name X and Y.

Lucas10101

Water = X
Calcium Carbide = Y

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Q. Name three impurities that normally exist in Calcium Carbide and how these could be removed? Give one use of Ethyne Gas?

Ethyne has three bonds in the C2H2, and is extremely unsaturated. Benzene C6H6 has many double bonds which also should make it unsaturated but is found to be very unreactive. Both are soluble in Cyclohexane but are insoluble in water. C2H2 makes Bromine colourless.

(i) Distinguish between Saturation and Unsaturation?
(ii) Why is Benzene so reactive if it has conditions for unsaturation?
(iii) How is Benzene normally represented as drawn?
(iv) Why are they insoluble in water?
(v) Why does Bromine go colourless and what's this a test for?
(vi) Would Iodine dissolve Methylbenzene? Give the property of Iodine that justifies your answer? Name a suitable substance that gives the opposite result to that obtained in part 1 of question (vi).

madnirvana

Q. Name three impurities that normally exist in Calcium Carbide and how these could be removed? Give one use of Ethyne Gas?

calcium Sulfide, Calcium phosphide, calcium nitride..
removed by bubbling through soln of copper sulfate .


Use = welding and cutting

Ethyne has three bonds in the C2H2, and is extremely unsaturated. Benzene C6H6 has many double bonds which also should make it unsaturated but is found to be very unreactive. Both are soluble in Cyclohexane but are insoluble in water. C2H2 makes Bromine colourless.

(i) Distinguish between Saturation and Unsaturation?
if turns bromine water yellowish red turns colourless +> its unsaturated.
forms a soln dibromeothanol


(ii) Why is Benzene so reactive if it has conditions for unsaturation?
because of electron clowds and pi bonds..
i am not very sure with this one.


(iii) How is Benzene normally represented as drawn?
circle in a hexagon

(iv) Why are they insoluble in water?
hydrogen bonding


(v) Why does Bromine go colourless and what's this a test for?
unsaturation.....


(vi) Would Iodine dissolve Methylbenzene?
yes/// both non polar ?


Give the property of Iodine that justifies your answer?
non polar?


Name a suitable substance that gives the opposite result to that obtained in part 1 of question
i dunnoconfused:

Lucas10101

Electronegativity is defined as the relative attraction that the shared pair of electron have for the covalent bonds in an atom. Atomic Radius is defined as half the distance between two nuclei of atoms that are joined by a single covalent Bond. Ionisation Energy is the defined as the energy to remove the most loosely bound electron from a neutral gaseous atom.

Q.
(i) What unit is Ionisation Energy measured in?
(ii) Account for the changes in Atomic Radii going across a period?
(iii) Account for for the changes in Electromegativity values going down a group?
(iv) Going down a group, account for the Reactivity of Group 1 in the Periodic Table?

( 30 Marks LCH Sample Paper)