Mark scheme for my teachers chemistry paper ( updated version)

the old version had some errors in some questions, after going through the paper myself again, i corrected these mistakes.

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  • Created on: 05-01-12 16:53
Preview of Mark scheme for my teachers chemistry paper ( updated version)

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Mark scheme for my teachers chemistry paper ( written by me)
Q1. A. Isotope= atoms of the same element with a different number of neutrons
b. requires you to complete this table
c. Carbon 12 (1)
e. Emperical formula :simplest whole ratio of atoms in a molecule (1)
Q2. A. 1. Ionic bond : electrostatic attraction between oppositely charged ions (1)
Covalent bond : electrostatic attraction on a shared pair of electrons (2)
b. electronegativity : the ability of an atom to attract electrons in a covalent bond (1)

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Q3.
b. Silicon has a giant covalent structure which is strong, as giant covalent bonds have to broken which requires
much energy. However, Sulphur has a simple molecular structure with simple van der waals forces between
molecules which are weaker than covalent bonds, so little energy is required to break them.…read more

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Al3+ and the delocalised electrons than between Na+ and the
delocalised electrons. ( 2 marks)
Using oil rig : In MnO2 the oxidation number of Mn is +4 and goes to +2 in MnCl2 reduction is gain of electrons, Mn
has gained electrons so its Mn that is reduced. (2) ( oxidation numbers correct and element which is reduced correct)
( species =1 mark , all state symbol =1 mark)
ii.…read more

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First ionisation energy : energy required to remove 1 electron from each atom in 1 mole of electrons to form 1
mole of gaseous 1+ ions.…read more

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State symbols and correct equation = 2 marks
iii. there is a leap between the 6th and 7th ionisation energies showing start of a new shell .…read more

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I pyramidal (1)
ii. 3 bond pairs , 1 lone pair, the lone pair repels slightly more than the bond pairs which results in the angle of 107
degrees( 3)
Q7. A. I because they have different numbers of protons in the nucleus
ii. the s block
iii. less because barium has more electrons and there is also more positive protons in the nucleus .which experience
greater atomic attraction, the nucleur charge increases and there is also shielding remains the same.…read more

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Good conductor because : there are free delocalised electrons between the layers which can move. Covalent
bonding exists between atoms in the layers.
High melt+boil point : because strong covalent bonds must be broken, which requires a lot of energy
Insoluble in water : non polar so not soluble
QRC : any three words spelled correctly and used in context correctly : conductivity, ions, covalent bonds, polar, ionic
bonds, delocalised electrons.…read more

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