Chemical Formulae, Equations And Calculations
Visão Geral
Chemical equations are the language chemists use to describe what happens during a reaction, and the calculations that follow let you predict exactly how much product you will make from a given amount of reactant. These skills underpin every topic in the rest of the course, from acids and bases to organic chemistry.
This lesson covers word and symbol equations, relative formula mass, the mole concept, reacting mass calculations, percentage yield, empirical and molecular formulae, solution concentrations, and gas volume calculations. Mastering these will give you the quantitative toolkit that Edexcel tests heavily across both Paper 1 and Paper 2.
Objetivos
- write word equations and balanced chemical equations (including state symbols): - for reactions studied in this specification - for unfamiliar reactions where suitable information is provided.
- calculate relative formula masses (including relative molecular masses) (Mr) from relative atomic masses (Ar)
- know that the mole (mol) is the unit for the amount of a substance
- understand how to carry out calculations involving amount of substance, relative atomic mass (Ar) and relative formula mass (Mr)
- calculate reacting masses using experimental data and chemical equations
- calculate percentage yield
- understand how the formulae of simple compounds can be obtained experimentally, including metal oxides, water and salts containing water of crystallisation
- know what is meant by the terms empirical formula and molecular formula
- calculate empirical and molecular formulae from experimental data
- understand how to carry out calculations involving amount of substance, volume and concentration (in mol/dm3) of solution
- understand how to carry out calculations involving gas volumes and the molar volume of a gas (24 dm3 and 24 000 cm3 at room temperature and pressure (rtp))
- practical: know how to determine the formula of a metal oxide by combustion (e.g. magnesium oxide) or by reduction (e.g. copper(II) oxide)
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Avaliação da Lição
Parabéns por concluir a lição em Chemical Formulae, Equations And Calculations. Agora que você explorou o conceitos e ideias-chave, é hora de colocar seu conhecimento à prova. Esta seção oferece uma variedade de práticas perguntas destinadas a reforçar sua compreensão e ajudá-lo a avaliar sua compreensão do material.
Irá encontrar uma mistura de tipos de perguntas, incluindo perguntas de escolha múltipla, perguntas de resposta curta e perguntas de redação. Cada pergunta é cuidadosamente elaborada para avaliar diferentes aspetos do seu conhecimento e competências de pensamento crítico.
Use esta secção de avaliação como uma oportunidade para reforçar a tua compreensão do tema e identificar quaisquer áreas onde possas precisar de estudo adicional. Não te deixes desencorajar pelos desafios que encontrares; em vez disso, vê-os como oportunidades de crescimento e melhoria.
- What is the relative formula mass (Mr) of sulfuric acid, H2SO4? (Ar: H = 1, S = 32, O = 16) A) 96 B) 98 C) 100 D) 49 Answer: B
- How many moles are in 4.4 g of carbon dioxide, CO2? (Ar: C = 12, O = 16) A) 0.05 B) 0.20 C) 0.10 D) 1.0 Answer: C
- At room temperature and pressure, what volume does 0.50 mol of any gas occupy? A) 6 dm3 B) 12 dm3 C) 24 dm3 D) 48 dm3 Answer: B
- A reaction has a theoretical yield of 25.0 g but only 20.0 g of product is collected. What is the percentage yield? A) 125% B) 80% C) 75% D) 20% Answer: B
- Which of these is the empirical formula of a compound with the molecular formula C6H12O6? A) C6H12O6 B) C3H6O3 C) CH2O D) CHO Answer: C
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Explain the concept of stoichiometry as it pertains to chemical reactions
"Chemistry: Reaction Stoichiometry" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/chemistry/pages/4-3-reaction-stoichiometry. Access for free at https://openstax.org/books/chemistry/pages/1-introduction
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Determining Empirical and Molecular Formulas
Compute the percent composition of a compound
"Chemistry: Determining Empirical and Molecular Formulas" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/chemistry/pages/3-2-determining-empirical-and-molecular-formulas. Access for free at https://openstax.org/books/chemistry/pages/1-introduction
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