2811_Jan_01MS

2811_Jan_01MS - OCR Advanced Subsidiary GCE in Chemistry...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
OCR Advanced Subsidiary GCE in Chemistry 2811 January 2001 Chemistry Foundation Page 1 of 1 3882 January 2001 2811 Jan 2001MS.doc 18/02/2001 Subject: Chemistry Foundation Code: 2811 Session: January Year: 2001 Final Mark Scheme 14th Jan 2001 MAXIMUM MARK 90
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
OCR Advanced Subsidiary GCE in Chemistry 2811 January 2001 Chemistry Foundation Page 4 of 4 3882 January 2001 2811 Jan 2001MS.doc 18/02/2001 Answer all questions 1. Lithium was discovered in 1817 by the Swedish chemist Arfvedson. Lithium exists naturally as a mixture of isotopes. (a) Explain the term isotopes . Atoms of the same element with different masses/ Same atomic number, different number of neutrons/ Atoms of the same element with different numbers of neutrons ± Response must imply atoms [1] (b) Which isotope is used as the standard against which relative atomic masses are measured? carbon-12 ± [1] (c) The mass spectrum below shows the isotopes present in a sample of lithium: (i) Use this mass spectrum to help you complete the table below for each lithium isotope in the sample. number of isotope percentage composition protons neutrons 6 Li 9 to 6 3 3 7 Li 91 to 94 3 4 mark must add up to 100 ± ± ± [3] (ii) Calculate the relative atomic mass of this lithium sample. Your answer should be given to three significant figures. 8 x 6/100 + 92 x 7/100 ± = 6.92 ± ( 91/9 6.91; 93/7 6.93; 94/6 6.94) [2] (d) The species responsible for the peaks in this mass spectrum are lithium ions, produced and separated in a mass spectrometer. (i) How are the electrons removed from lithium atoms to form lithium ions in a mass spectrometer? (bombarded) with electrons ± [1] (ii) How does a mass spectrometer separate the ions? (deflected by) a magnet(ic field) ± [1] For last 2, mark by column or row
Background image of page 2
OCR Advanced Subsidiary GCE in Chemistry 2811 January 2001 Chemistry Foundation Page 5 of 5 3882 January 2001 2811 Jan 2001MS.doc 18/02/2001 (e) The first ionisation energy of lithium is +520 kJ mol 1 . (i) Define the term first ionisation energy . Energy change when each atom in 1 mole ± of gaseous atoms ± loses an electron ± (to form 1 mole of gaseous 1+ ions). [3] (ii) The first ionisation energy of sodium is +496 kJ mol 1 . Explain why the first ionisation energy of sodium is less than that of lithium. Your answer should compare the atomic structures of each element. electron is further from nucleus/ electron in a different shell ± electron experiences more shielding ± nuclear attraction decreases/distance or shielding outweighs nuclear attraction/ effective nuclear charge is less ± [3] [Total: 15]
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
OCR Advanced Subsidiary GCE in Chemistry 2811 January 2001 Chemistry Foundation Page 6 of 6 3882 January 2001 2811 Jan 2001MS.doc 18/02/2001 2. Electrons are arranged in energy levels. The diagram below is incomplete. It shows two electrons in the 1s level. (a) Complete the diagram for the 7 electrons in a nitrogen atom by (i) adding labels for the other sub-shell levels, [1] (ii) showing how the electrons are arranged. [2] [3] (b) Magnesium reacts with nitrogen forming magnesium nitride, which is an ionic compound.
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 10

2811_Jan_01MS - OCR Advanced Subsidiary GCE in Chemistry...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online