Determining an equation from given values
Lesson details
Learning outcome
I can deduce the balanced symbol equation from the masses of reactants and products of a given reaction.
Key learning points
- The stoichiometry of a chemical reaction is the molar ratio of each substance in a balanced symbol equation.
- Stoichiometric values can be calculated using masses found by experiment.
- Subscript values in chemical formula indicate the ratio of atoms/ions in a molecule/formula unit.
Keywords
Balanced symbol equation - Describes a reaction using a symbol equation with coefficients, which ensure there are equal numbers of atoms of each element on both sides of the symbol equation.
Stoichiometry - Refers to the molar ratio of the reactants and products in a chemical reaction.
Mole - A mole of something is 6.02 × 10²³ of it. The mass of a mole of a substance is its relative mass expressed in grams.
Ratio - Ratio can be used to determine the size of one quantity in relation to another.
Common misconception
Some pupils incorrectly interpret subscript and stoichiometric values in a balanced symbol equation.
Both subscript and stoichiometric values represent ratios. Subscripts indicate ratios *within* substances; stoichiometry. Molar ratios *between* substances in a reaction. Much practice distinguishing between/ interpreting these is time well spent.
Teacher tip
The process of ratios is a frequent feature of calculations in chemistry. If not part of the course already, consider extending this idea to incorporate empirical formula calculations.
Licence
Lesson video
Loading...
Prior knowledge starter quiz
6 Questions
Q1.A beaker contains six pens. Three pens are black, two are red and one is green. Which of the follow ratios are correct?
Q2.Which empirical formula shows a metal to non-metal ratio of 1 : 2?
Q3.True or false? The unit for relative atomic mass is grams.
Q4.State the unit for amount of substance.
Q5.When a chemical is __________ there will always be some left over at the end of the reaction.
Q6.Calculate the relative formula mass of ammonium nitrate, NH₄NO₃. Relative atomic masses: N = 14; H = 1; O = 16.
Assessment exit quiz
6 Questions
Q1.The formula for sulfuric acid is H₂SO₄. What is the ratio of oxygen to sulfur in the formula?
Q2.Which of the following chemical equations shows a similar molar ratio to the reaction?:
Ca(OH)₂ + 2HNO₃ → Ca(NO₃)₂ + 2H₂O
Q3.6 moles of calcium hydroxide, Ca(OH)₂, react with excess nitric acid, HNO₃. How many moles of water are formed in the reaction?
Ca(OH)₂ + 2HNO₃ → Ca(NO₃)₂ + 2H₂O
Q4.0.5 g of magnesium reacts with oxygen to form 0.8 g of magnesium oxide. Calculate the number of moles of magnesium oxide formed during the reaction. Relative atomic masses: Mg = 24; O = 16.
Q5.What is the reacting ratio when 12.0 g of magnesium, Mg, reacts with 8.0 g of oxygen, O₂, to produce magnesium oxide?
Q6.It is possible to determine the balanced symbol equation of a reaction from the molar ratios using the following step. Place the steps into the correct order.
To help you plan your 10 combined science lesson on: Determining an equation from given values, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 combined science lesson on: Determining an equation from given values, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 combined science lessons from the Calculations involving masses unit, dive into the full secondary combined science curriculum, or learn more about lesson planning.