Topic 3-Quantitative Chemistry Flashcards
What is the explanation for an increase in mass in a reaction?
One of the reactants may be a gas thats found in air.
Before the reaction the gas is floating around in the air but it is not in the reaction so you cant account for its mass.
When the gas reacts it forms part of the product it is contained inside of the reaction so the total mass inside the reaction increases.
What is the explanation for if the mass decreases in a reaction?
Because one or more of the products are gases.
Before the reaction all the reactants are contained in the reaction.
If the reaction isnt enclosed the gases can escape the reaction. They are no longer contained in the reaction so you cant account for their mass. So the total stuff inside the reaction decreases.
Why do reactions stop?
When one of the reactants are used up and any other reactants are in excess.
The reactant that is used up is called the limiting reactant.
The amount of product formed is directly proportional to the amount of limiting reactant.
This is because if you add more reactant there will be more reactant particles to take part in the reaction which means more product particles.
