ICT SKILLS
Simulating chemical reactions INTERPRETING CHEMICAL EQUATIONS
On this first page, we show you two tools that will help you practice balancing chemical reactions and understand the proportion of the reacting substances
BALANCING CHEMICAL EQUATIONS We will use an application available on the Anaya website. The application has two parts: Introduction and Play. • The application lets you balance chemical equations in a visual and intuitive way. It continually updates the number of atoms of each element in the reactants and products. To begin, use the Introduction part: activate the tool in the upper right that lets you visualise the balance of elements.
given the amount of products and reactants at the end of the reaction. In future years, this will help us understand the concept of the limiting reactant.
REACTANTS, PRODUCTS AND LEFTOVERS We will now use an application that complements the previous one. You can download it at https://phet.colorado.edu/en/simulation/ reactants-products-and-leftovers. It begins with an example of 2:1 stoichiometry: making a sandwich requires 2 slices of bread and 1 slice of cheese. It seems simple but this is the idea we will use to predict which reactant will be leftover.
• Note that the number of molecules, or fundamental units, must be a whole number in this application. • Use Play to raise the level of difficulty of the equations to balance. If you do not succeed with a problem, the application will give you the option to guess why and make a new attempt, as shown in the picture:
Understand, think, search… 1 Explain why the the coefficient of the simple or elemental substances should be adjusted last.
Once we have worked with the application, we must take a step beyond and see what happens in situations where the fundamental units of the reactants are not in stoichiometric proportions.
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2 In the same way that when we have four slices of bread and just one of cheese, the cheese ‘limits’ how many sandwiches we can prepare (just one). In stoichiometry we use the concept of the ‘limiting reactant’, which we will study in more depth in future years. If we take the example of the formation of ammonia and we have two mole of nitrogen (N2) and three of (H2), which is the limiting reactant?
