Determining an equation experimentally: sodium hydrogencarbonate
Lesson details
Learning outcome
I can describe a safe experiment to calculate the stoichiometric values for the decomposition of sodium hydrogencarbonate.
Key learning points
- Heating sodium hydrogencarbonate in a crucible leads to its decomposition.
- The risk involved with heating sodium hydrogencarbonate is low.
- The stoichiometry for a reaction can be calculated given experimental data.
- Because a gas is not a reactant in this reaction, the crucible lid remains closed throughout the heating process.
Keywords
Decomposition - A type of reaction where a reactant compound breaks down into two or more products.
Ratio - A ratio can be used to determine the size of one quantity in relation to another.
Stoichiometry - The molar ratio of the reactants and products in a chemical reaction.
Mole - 1 mole of a substance is 6.02 × 10²³ particles of it. The mass of a mole of a substance is its relative mass in grams.
Balanced symbol equation - A reaction using a symbol equation with coefficients to ensure there are equal numbers of atoms of each element on both sides of the equation.
Common misconception
Pupils may think that the mass of the crucible and contents will not change during the reaction because the lid is closed, believing that all gases produced remain inside.
Explain that even with the crucible lid on, gases like carbon dioxide & water vapour formed during decomposition can escape around the edges. This leads to a decrease in mass, which is crucial for calculating the stoichiometry based on the mass loss.
Teacher tip
This lesson presents a fantastic opportunity to bring together multiple aspects of the topic – types of reactions, conservation of mass, moles, ratios, practical skills, equipment choice, etc. Opportunities to adapt it to the needs of the class/provide extension activities is extensive!
Equipment
Sodium hydrogencarbonate, spatula, weighing boat, balance, crucible + lid, clay triangle, tripod, Bunsen burner, heatproof mat, tongs.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.The formula for sodium hydrogen carbonate is NaHCO₃.
Which of the following statements about sodium hydrogen carbonate are correct?
Q2.What is the ratio of sodium hydrogen carbonate to water in the following equation?
2NaHCO₃ → Na₂O + 2CO₂ + H₂O.
Q3.Which of the following equations shows the correct relationship between moles, mass and relative mass?
Q4.What type of reaction does the following chemical equation represent?
CuCO₃ → CuO + CO₂.
Q5.Calculate the relative formula mass of sodium hydrogen carbonate, NaHCO₃.
Relative atomic masses: Na = 23; H = 1; C = 12; O = 16.
Q6.Calculate the mole sof 4.2 g of sodium hydrogen carbonate, NaHCO₃.
Relative formula mass of NaHCO₃ = 84.
Assessment exit quiz
6 Questions
Q1.Match the following key terms to their definition.
A reaction where a reactant breaks down into two or more products.
The unit for amount of substance.
No substances can enter or leave.
The mass of the reactants equals the mass of the products.
Ratio of particles that react/form in a chemical reaction.
Q2.When sodium hydrogen carbonate is heated in a crucible it into sodium oxide, carbon dioxide and water.
Q3.Why can the crucible lid remain closed during the following reaction?
2NaHCO₃ → Na₂O + 2CO₂ + H₂O.
Q4.5.0 g of sodium hydrogen carbonate was heated in a crucible. At the end of the reaction, 2.3 g of solid remained. Calculate the mass of gaseous products produced during the reaction.
Q5.Which of the following is the balanced symbol equation for the thermal decomposition of sodium hydrogen carbonate into sodium hydroxide and carbon dioxide?
Q6.Calculate the maximum mass of sodium hydroxide (NaOH) that can be formed from 2.00 g of sodium hydrogen carbonate during the following reaction:
NaHCO₃ → NaOH + CO₂
RFM: NaHCO₃ = 84; NaOH = 40.
To help you plan your 10 combined science lesson on: Determining an equation experimentally: sodium hydrogencarbonate, 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 experimentally: sodium hydrogencarbonate, 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.
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The assessment exit quiz will test your pupils' understanding of the key learning points.
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