3. Quantitative chemistry (moles, limiting reactant, concentration of solutions) Flashcards
What does the law of the conservation of mass state?
No atoms are made or lost during a chemical reaction
mass of reactants = mass of products
If a reaction seems to involve a change in mass, what should you check for?
a reactant or a product as a gas and if its mass has not been taken into account
If the mass of reactants = mass of products, then how can chemical reactions be represented?
As balanced symbol equations
Why might a gas’ mass not be taken into consideration?
because the gas has been released into the atmosphere
What are chemical amounts measured in?
moles
What are the units for moles?
mol
What is the mass of 1 mole of a substance equal to?
it’s relative atomic mass
What does 1 mole of a substance and 1 mole of any other substance contain?
the same number of the stated particles, atoms, molecules or ions
What is Avogadro’s constant?
The number of atoms, molecules or ions in a mole of a given substance
What is the value of Avogadro’s constant?
What is the equation for number of moles?
Moles = Mass / Mr
What do the big numbers in front of chemical formulas tell you?
How many moles of each substance there is
What can masses of reactants and products be calculated from?
balanced symbol equations
What must be the same on both sides of the equation?
the total moles of 1 element
What is the limiting reactant?
the reactant that is used up/not in excess
Why is the limiting reactant called the limiting reactant?
Since it limits the amount of products
When does a reaction stop?
When all of one of the reactants is used up
How can you find out the mass of a product formed in a reaction with the limiting reactant?
The mass of the limiting reactant is equal to the mass of the product formed
In a chemical reaction involving two reactants, what will often happen?
you will often use one in excess to ensure that all of the other reactant is used
What can the concentration of a solution be measured in?
g/dm3
How do you calculate the mass of a solute in a given volume of a known concentration?
mass = conc x volume
What gives a higher concentration?
a smaller volume or larger mass of solute
What gives a lower concentration?
a larger volume or smaller mass of solute
What is the equation for concentration?
What is the equation for concentration involving moles?
