Studied by 0 peopleWhy is Avogrado's Constant used?
The mass of 6.02 x 10^23 of any substance will be the same number as the substance's relative formula mass in grams
What does all of this mean?
1 mole of a substance = that substances relative formula mass in grams
What does the Conservation of Mass concept state? What does this mean?
In a chemical reaction no atoms are created or destroyed, only the bonds between these atoms change, mass is always conserved.
This means that the total mass of the reactants in a reaction should be the same as the total mass of the products
What are reacting masses?
The mass of each reactant and product in a reaction
Why is a limiting reactant called a limiting reactant?
It limits the amount of product made
What are other reactants besides the limiting reactant referred to as?
In excess
What is relative formula mass?
The average mass of an entire compound
How to find out relative formula mass?
Add together the relative atomic masses of all the atoms in a compound's formula
What is a mole?
The unit used to measure the amount of a chemical
What is 1 mole of a substance?
6.02 x 10^23 particles
EXAMPLE
What would 1 mole of carbon mean?
That there are 6.02 x 10^23 atoms of carbon
What is the exception to this rule?
If your reaction involves a gas and is done in an open system , the mass might seem to change as the gas may come from the air or float off into the air and can't be measured.
Why might the mass seem to increase during a reaction (higher product mass than reactant)?
One of the reactants is a gas that is found in the air and all the products are solids, liquids or aqueous.
Before the reaction gas is floating around in the air so therefore it cannot be physically contained as a reactant as it ia a gas and its mass cannot be measured
When the reaction happens, the gas becomes physically contained into one of the products (E.g Metal oxide) so its mass can now be measured as it is a part of a solid, liquid or aqueous product and it isn't just a gas on its own - meaning the total mass of the products seem higher than the mass of reactants.
Why might the mass seem to decrease during a reaction (higher reactant mass than product)?
One of the products of a reaction is a gas.
Before the reaction all the reactants are solid, liquid or aqueous.
If your reaction is done in an open system and one of your products is a gas, this gas escapes into its surrounding as it is formed and isn't physically contained meaning its mass cannot be measure - this means that the total mass of products seems lower than the total mass of the reactants.
What do the big number before the formulas of the reactants and products in a reaction show?
The number of moles of each substance and the ratio of moles of each substance
What can you use reacting masses for?
To balance an equation.
When does a reaction stop?
When one of the reactants is completely used up
What is this reactant called?
The limiting reactant
What is the relationship between the amount of the limiting reactant and the amount of product made?
The amount of limiting reactant is directly proportional (the same as) the amount of product produced.
Note
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