Topic #3: Quantitative Chemistry Flashcards
What is the law of conservation of mass?
No atoms are lost nor made in a chemical reaction, therefore mass of reactants = mass of products
What does balancing equations do?
Ensures the same number of atoms are on both sides of the equation
What is the Mr of a molecule?
The sum of the relative atomic masses in said molecule
What is the volume of 1 mole of any gas at room temperature?
24dm^3
Why could some reaction seem as if the mass changed?
One product could be a gas that escaped or isn’t being measured
What is the mass of 1 mole of a substance?
Its Mr
What is Avogadro’s constant?
The number of atoms in a mole of something (6.02 x 10^23 per mole.)
Give the formula linking mass, moles and Mr
Mass = Mr x moles
What does the number next to a molecule represent? eg. 2NaCl
The no. of moles of that substance
How to balance equations using moles?
Calculate a molar ration with the formula and add the numbers as appropriate
What is a limiting reactant?
Ina reaction it is common to use an excess of one reactant with another reactant to use all of it up. The completely used up reactant is the limiting reactant.
What is the formula for calculating concentration of solutions?
Concentration = moles / volume Concentration = mass / volume
What is percentage yield and how is it calculated?
It is the amount yielded from a reaction divided by the expected amount (or maximum theoretical mass), x100
It works out how much we got from what we expected
What is atom economy and how is it calculated?
It is how many atoms ended up as the desired product
Mr of desired product / Mr of all reactants, x100
How do you perform a titration?
Add a solution and some indicator to a conical flask. Then add the second chemical, mark where it’s volume is on the burette, then add it bit by bit, swirling the flask each time. Keep going until the indicator changes colour to neutral, then record the volume difference.
