An atom of element X has a mass number of 27 and contains 14 neutrons. How many electrons are present in the ion ?
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WAEC Chemistry
2 papers150 marks3 h
What we predict comes up
From the syllabus weighting and how the papers are usually set. The papers below follow it.
- Stoichiometry and the mole16%Mole calculations run through the whole paper: masses, concentrations, empirical formulae and gas volumes at s.t.p.
- Atomic structure and the periodic table15%Electronic configuration, isotopes, periodic trends and radioactivity appear in most objective papers and often anchor a Section B question.
- Energy, rates and equilibrium14%Enthalpy changes, Hess's law, collision theory and Le Chatelier's principle applied to industrial equilibria form a common long question.
- Acids, bases and salts12%Definitions, pH, salt types, salt preparation and a volumetric analysis calculation are a regular Section B question.
Paper 1: Objective
1 h · 50 marks · Calculator allowed
- Answer all the questions.
- Each question is followed by four options lettered A to D. Choose the correct option for each question.
- Each question carries one mark.
- Where needed, use: H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Ca = 40, Cu = 64. Molar volume of a gas at s.t.p. = 22.4 dm³. Faraday constant = 96 500 C mol.
Answer or mark a question and your score adds up here.
Answer all questions50 marks
Which of the following is the electronic configuration of an atom of atomic number 17?
Naturally occurring chlorine consists of 75% of and 25% of . What is the relative atomic mass of chlorine?
47 more questions
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Not included: Paper 3, the practical test (titration, qualitative analysis and tests for ions and gases), is not included because it is sat at the bench.