7 Questions
What should be done if any of the numbers obtained from dividing the moles are not whole numbers?
Multiply all the numbers by the same amount so that they all become whole numbers, and then write the balanced symbol equation for the reaction by putting these numbers in front of the chemical formulas.
If you know the masses of the reactants and products that took part in a reaction, what can you work out?
The balance symbol equation for the reaction.
What should be done next after finding the number of moles of each substance in a reaction?
Divide the number of moles of each substance by the smallest number of moles in the reaction.
What is the first step in working out the balance symbol equation for a reaction?
Divide the mass of each substance by its relative formula mass to find the number of moles.
When can you tell a reaction has taken place when magnesium carbonate is placed into a beaker of hydrochloric acid?
You can tell a reaction has taken place because you can see lots of bubbles of gas being given off.
What is the purpose of adding reactants in excess?
Reactants are added in excess to make sure that the other reactant is completely used up in the reaction. The reactant that is used up is called the limiting reactant.
When does the reaction stop in the presence of excess reactants?
The reaction stops when all of one of the reactants is used up, while the other reactants are in excess.
Study Notes
Stoichiometry and Chemical Reactions
- If the numbers obtained from dividing the moles are not whole numbers, it indicates that the equation is not balanced, and adjustments need to be made.
Calculating Reaction Quantities
- If you know the masses of the reactants and products that took part in a reaction, you can work out the number of moles of each substance and the mole ratio of the reactants and products.
Balancing Chemical Equations
- After finding the number of moles of each substance in a reaction, the next step is to use the mole ratios to balance the symbol equation.
Writing Balanced Equations
- The first step in working out the balance symbol equation for a reaction is to write the unbalanced symbol equation, using the chemical formulas of the reactants and products.
Identifying Chemical Reactions
- A reaction has taken place when magnesium carbonate is placed into a beaker of hydrochloric acid if you observe bubbling or the formation of a gas.
Limiting Reactants and Excess Reactants
- The purpose of adding reactants in excess is to ensure that the limiting reactant is completely consumed, allowing the maximum amount of product to be formed.
- The reaction stops in the presence of excess reactants when the limiting reactant is completely consumed, and no more product can be formed.
Mastering Mole Calculations: Test Your Skills in Balancing Symbol Equations
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