Quantative Chemistry - P1 Flashcards
What is the law of conservation of mass?
No mass is created or destroyed in a reaction
How do you work out the mass of a product from a reaction?
Combine the masses of all the components
How do you calculate the mass of a component in a reaction?
Subtract the mass of all other components from the product’s mass
When are ionic compounds formed?
When metals react with non - metals
What are ions?
Atoms with a charge
What type of ions do most non - metals form?
Negative ions
Charge of a metal ion is often the same as the ___ ?
Group number
Transition metals can form ___
Several ions
Which non - metals form positive ions?
Hydrogen and Ammonium
What must charges do in an ionic compound?
Cancel out
How do you balance a chemical equation?
Look at each atom in the equation and count the amount on either side. Add the correct amount of atoms to either side.
What is relative atomic mass?
The weight of an element, taking into account the abundance of each isotope
How do we find relative atomic mass?
By adding the masses of all the isotopes (taking into account abundance)
What is relative formula mass?
The sum of the relative atomic masses of the atoms in a formula
Relative formula mass has no ___ ?
Units
Relative formula mass never uses ___ ?
Big numbers
How to calculate percentage mass?
Divide relative atomic mass by relative formula mass.
What is 1 mole equal to?
1 mole = Relative atomic mass of an element
How to work out moles in a compound?
mass (g) / relative formula mass
How to work out moles in an element?
mass (g) / relative atomic mass
What is avagadro’s contstant?
1 mole (6.02x10^23)
How do you use avagadro’s constant to work out the number of atoms in a formula?
- Count atoms in formula
- Calculate amount of moles (weight / relative formula mass)
- Multiply by avagadro’s constant.
What is a limiting reactant?
A reactant that get used by before the others.
What is an excess reactant?
A reactant that is left over after the limiting reactant has been fully reacted
How do you work out the concentration of a solution?
mass/dm3
How do you calculate percentage yield?
Work out how many moles of reactant there are (mass/Ar)
Multiply amount of moles by product’s Ar / Mr to get the product’s theoretical mass
(product made / theoretical mass) x 100 = percentage yield.
Why is it not always possible to achieve 100% yield in a reaction?
Some product may be lost when separated from the reaction mixture
Some reactants may react in different ways, producing unexpected results
Reversible reactions may not go to completion
We cannot achieve _____.
more than 100% yield, as we would otherwise be creating atoms.
How do you calculate the number of moles in a volume of a solution?
Divide concentration by volume.
How do you calculate the mass of a solution?
Multiply concentration by volume to get number of moles
Multiply number of moles by solution Mr to get mass.
One mole of any gas occupies of a volume of ____.
24dm^3 at 20c and a pressure of 1 atmosphere.
