Chemistry Y11

What is a mole?

A unit used to measure an amount of substance

How many particles are in one mole?

6.02 × 10^23 particles - the Avogadro constant

What types of particles can be counted using moles?

Atoms, molecules, ions or electrons

What is the equation linking mass, relative formula mass and moles?

Mass = Mr x Moles

When using Avogadro's constant, what's the difference between finding molecules/formula units and finding atoms/ions?

Molecules/formula units: moles x Avogadro's constant

Atoms/ions: first calculate the number of molecules/formula units, then multiply by the number of that atom/ion in each particle

2 mol of H₂O contains how many molecules and how many hydrogen atoms?

Molecules: 2 x 6.02 x 10^23 = 1.204 × 10^24
Hydrogen atoms: 1.204 x 10^24 x 2 = 2.408 x 10^24

Balance out the following equation and state each of the masses:
HCl + Mg → MgCl2 + H2

2 HCl + Mg → MgCl2 + H2
HCl = 73g, Mg = 24g, MgCL2 = 95g, H2 = 2g

How can you balance an equation using masses and Mr?

Calculate moles of all substances, write the mole values in a ratio, divide every value in the ratio by the smallest value, the numbers in the ratio determine the big numbers in front of the substance

8.5G of NaNO3 reacts to form 6.9g of NaNO2 and ?g of O2
Calculate the mass of O2 and write a balanced symbol equation using masses and Mr

O2 = 1.6g
2NaNO3 → 2NaNO2 + O2

When using masses and Mr to balanced a symbol equation, what is something key about the ratio?

There must be no decimals, you must multiply to get whole numbers

In a reaction, the reactant that is completely used up is the ____________ → Limits the amount of ________

Limiting reactant, products

How do you determine the limiting reactant of a reaction?

Work out the moles of a substance, which ever is lower is the limiting factor

You have 0.18 mol of CaO and 0.56 mol of H20, what sentence would you write to show the limiting reactant?

If i had 0.18 mol of CaO, I would need 0.18 mol of H20, so I have excess H20 and CaO is the limiting reactant