Concept explainers
4.24 Ammonia gas can be prepared by the reaction
If 112 g of CaO reacts with 224 g of NH4Cl, how many moles of reactants and products are there when the reaction is complete?
Interpretation:
To calculate how many moles of reactants and products will be left after the completion of reaction.
Concept introduction:
- Reactants decrease in moles, Products increase in moles.
- Stoichiometry relates all species to their atomic ratios.
- Limiting reactant will never be leftover if 100 % completion.
- Excess reactant will always be leftover.
Given:
Answer to Problem 4.26PAE
Solution:
Explanation of Solution
When a reaction occurs, there are reactants reacting in order to form new products. The reactants are not typically added in a 100 % stoichiometric ratio, therefore, there is always a limiting and an excess reactant.
It is much easier to convert to molar units, rather than mass units, in order to verify the reactants and products present.
Step 1: Balance Reaction
The reaction is already balanced
Step 2: Change all mass units to mol units
Step 3: Relate stoichiometry
Step 4: Moles reacted
Identify the limiting reactant (
Excess reactant of
Step 5: Moles produced
Moles of product
Moles of product
Moles of product CaCl2 formed
Use stoichiometry to verify the ratio between species, that is, reactants and products after the reaction is over.
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