Chem

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  • Created by: debbieox
  • Created on: 17-04-17 17:51
Describe the properties of fluorine, chlorine, bromine and iodine?
Fluorine is a pale-yellow gas, chlorine is a pale-green gas, bromine is a red liquid and iodine is a shiny grey solid.
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What is the trend in melting and boiling points going down group 7?
It increases going down the group as the molecules become larger, they have more electrons so have larger van der Waals forces between the molecules. As the intermolecular forces get larger, more energy is required to break the forces.
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What is the trend in electronegativity going down the group?
It decreases going down the group because the atomic radius increases due to the increasing number of shells. The nucleus is less able to attract the bonding pair of electrons.
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What is the trend in oxidising strength going down the group?
It increases going down the group because the molecules become larger so they have more shells so is less able to attract an electron.
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What does the reaction of halide ions with silver nitrate tell us?
It tells us which halide ion is present.
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How is the experiment to tell us what halide ion is present carried out?
The test solution is made acidic with nitric acid and then silver nitrate solution is added dropwise. The role of the nitric acid is to react with any carbonates present to prevent any formation of silver carbonate.
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How can we tell which halide ion is present?
Fluorides don't produce a precipitate, chlorides produce a white precipitate, bromides produce a cream precipitate and iodides produce a pale-yellow precipitate.
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Why would you add ammonia to these precipitates?
It helps us differentiate between them if the colours look too similar. Silver chloride dissolves in dilute ammonia, solver bromide dissolves in concentrated ammonia and silver iodide does not react with ammonia.
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What is the trend in reducing power going down the group?
It increases because the larger the ion, the easier it is to lose an electron as there is less attraction between the nucleus and the outer electron due to shielding.
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What are fluoride and chloride ions like as reducing agents?
They are not strong enough to reduce sulphur in sulphuric acid, an acid-base reaction occurs.
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What are bromide ions like as reducing agents?
Bromide ions are stronger than chloride and fluoride ions.
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What is the reaction of chlorine in water without sunlight?
Aqueous chlorine reacts with water to produce HClO (Aqueous) and hydrochloric acid.
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What is the reaction of chlorine in water with sunlight?
2Cl2 reacts with 2H2O to produce 4H+, 4Cl- and 02.
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What are the uses of chlorine?
It is used in water treatment to kill bacteria. It is also used to treat drinking water and the water in swimming pools. The benefits to health outweigh its toxic effects.
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What is the reaction of chlorine with cold, dilute NaOH solution?
Chlorine (as well as bromine and iodine) in aqueous solutions with react with cold sodium hydroxide. The colour of the halogen solution will fade to colourless. Cl2 + 2NaOH --> NaCl + NaCLo + H2O. The mixture of NaCl and NaClO is used as bleach.
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How do you work out atom economy?
Mass of wanted product / mass of all reactants x 100
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How do you work out percentage yield?
Mass obtained / theoretical mass x 100
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How do you work out the empirical formula?
Divide each mass by the atomic mass of the element. For each of the answers, divide them by the smallest answer you first got. You may need to round afterwards.
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What does T stand for?
Temperature in K
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How can you work out the number of moles in a solution?
n = concentration x volume
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How can you work out the number of moles?
n = mass / Mr
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How do you get from dm^3 to m^3?
/1000
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How do you get from cm^3 to m^3?
/1000000
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What does n stand for?
Number of moles
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What does R stand for?
The gas constant
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What is the ideal gas equation?
PV = nRT
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What does P stand for?
Pressure in kPa
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How do you get from kPa to Pa?
x 1000
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What does V stand for?
Volume in m^3
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What are the relative masses, charges and location of protons, neutrons and electrons?
Protons - mass = 1, charge = +1 and location is in the nucleus Neutrons - mass = 1, charge = 0 and location is in the nucleus Electron - mass = 1/1840, charge = -1 and location is in the orbitals
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What is the mass number?
Total number of protons and neutrons (largest number)
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What is the atomic number?
Number of protons
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What is an isotope?
Atoms with the same number of protons but different number of neutrons
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Explain ionisation in the mass spectrometer.
The sample that is being investigated is dissolved in a volatile solvent and is forced through a fine hollow needle that is connected to the positive terminal of a high voltage supply.
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Explain acceleration in the mass spectrometer.
The positive ions are attracted towards the negatively charged plate at the end of the spectrometer and accelerate towards it. Lighter ions and more highly charged ions are faster.
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Explain the flight tube in the mass spectrometer.
The ions travel along the flight tube and their time of flight is recorded.
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Explain the detection in the mass spectrometer.
When the lighter ions hit the detector plate first, a current is produces as the positive ions pick up an electron from the detector.
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How do you calculate the average relative atomic mass of the graph?
(% abundance x m/z) + (% abundance x m/z)/ total abundance
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What are exceptions in electron arrangement?
4s orbital is filled up before the 3d orbital because it is of lower energy. Therefore vanadium is 1s2 2s2 2p6 3s2 3p6 3d3 4s2
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What is the electron pair repulsion theory?
A theory which explains the shapes of molecules by assuming that pairs of electrons around a central atom repel each other and thus take up positions as far away as possible.
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What is a linear shape?
Two pairs around the central atom. They have an angle of 180 degrees.
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What is a trigonal planar shape?
Three pairs of electrons around the central atom. Angles are 120 degrees.
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What is tetrahedral shape?
Four pairs of electrons round the central atom. Angle is 109.5.
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What is trigonal bipyramid shape?
Five pairs of electrons round the central atom. It has a 90 degree angle and 120 degree angle.
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What is octahedral shape?
Six pairs of electrons around the central atom. Angles are 90 degrees.
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What is v-shape/bend shape?
2 bonding pairs and one lone pair. Angle is 104.5.
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Describe a giant structure.
Giant structures have ionic bonds and have high melting points. They only conduct electricity in liquid or aqueous solution states.
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Describe a giant macromolecular structure.
They have covalent bonds with a high melting point. Only graphite and graphene conduct electricity in solid form.
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Describe simple molecular structure.
It has covalent bonds with low melting points,
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Describe a giant metallic structure.
It has metallic bonds with high melting points. It will conduct electricity in solid state and liquid.
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What are standard conditions for an enthalpy change?
Pressure of 100kPa and temperature of 278K
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What is the standard enthalpy of formation?
The enthalpy change when one mole of substance is formed from its constituent elements under standard conditions with all reactants and products being in their standard states.
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What is the standard enthalpy of combustion?
The enthalpy change when one mole of substance is completely burnt in oxygen under standard conditions with all reactants and products being in their standard states.
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What is the equation for working out enthalpy change?
q=mcAt
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What is Hess's law?
The enthalpy change for a chemical reaction is the same regardless of the route that is taken from reactants to products.
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What is Le Chatelier's principle?
If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance.
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What happens to the equilibrium when you change the concentration
If you increase the concentration, equilibrium will shift to the side that decreases the concentration
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What is the effect of pressure on equilibrium?
Increasing pressure means that equilibrium will move to the side with fewer moles.
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What is the effect of temperature on equilibrium?
Increasing temperature means that equilibrium will shift in the endothermic direction.
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What is the Kc equation?
mA + nB makes pC + qD --- Kc = [C]^P [D]^Q / [A]^M [B]^N
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Effect of changing temperature.
Endothermic reaction - temp is decreased, Kc decreases, products decreases, reactants increase and equilibrium moves left --- Exothermic - temp increases, Kc decreases, products decrease, reactants increase and equilibrium moves left.
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What is an oxidising agent?
A reagent that oxidises another species - removes electrons from another.
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What is a reducing agent?
A reagent that reduces another species - adds electrons to
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What are the unusual oxidation states?
Hydrogen in metal hydrides, where it is always -1, eg. HCl - Oxygen in peroxides, where it is -1 and in OF2 where it is +2 - Chlorine when it is in compounds with F and O and it has a positive value.
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Other cards in this set

Card 2

Front

What is the trend in melting and boiling points going down group 7?

Back

It increases going down the group as the molecules become larger, they have more electrons so have larger van der Waals forces between the molecules. As the intermolecular forces get larger, more energy is required to break the forces.

Card 3

Front

What is the trend in electronegativity going down the group?

Back

Preview of the front of card 3

Card 4

Front

What is the trend in oxidising strength going down the group?

Back

Preview of the front of card 4

Card 5

Front

What does the reaction of halide ions with silver nitrate tell us?

Back

Preview of the front of card 5
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