Chapter 3-Amount of substance Flashcards
What is the Avogadro constant? (Nₐ)
6.02x10²³mol⁻¹
What is the formula for no. of moles?
Moles=Mass/Mr
What is an Empirical formula?
- The simplest whole-number ratio of atoms of each element in a compound
- e.g. C₆H₁₂O₆ would be CH₂O
How do you find the empirical formula of a substance?
Work out the moles of each substance and find the ratios between each element.
What are hydrated salts?
Crystalline salt molecules loosely attached to a certain number of water molecules
How do you display the formula of hydrated salts?
By using a . instead of a + sign between the ionic compound and
𝑥H₂O
How does a hydrated salt change, what does it form and what is it now called?
- It is heated
- It forms a powder
- It is called an anhydrous salt
What are the steps to finding out the composition of a hydrated salt?
1) Weigh empty crucible, add hydrated salt, reweigh and calculate mass of hydrated salt
2) Heat gently for 1 min then heat vigorously for 3 mins and leave to cool
3) Reweigh crucible and anhydrous salt then calculate the mass of anhydrous salt and the mass of water removed
4) Calculate moles of water removed and anhydrous salt at the end
5) Simplify ratio to 1: 𝑥 to find the no. of moles of water
What are the assumptions in the hydrated salt experiment?
- All of the water has been lost
- There had been no further decomposition
What is the ratio between moles of substances in an equation called?
The Stoichiometry
How do we calculate percentage yield?
(Actual yield/Theoretical yield)x100
What are the reasons for not getting a 100% yield?
- Impure reactants
- Side reactions
- Reaction may have been reversible
- Reaction may not have finished
- Product loss/spillage
What is atom economy?
The extent to which the atoms in the starting materials end up in the desired product?
What is the formula for atom economy?
(Amount of useful product Mr / Amount of reactants Mr) x 100
What does RTP stand for?
Room temperature and pressure
What is the RTP?
- 20°
- 100kPa
What is the molar gas volume?
The volume per mole of gas molecules at a given temperature and pressure
What is the volume of one mole of gas at RTP?
24dm³ / 24000cm³
What is the ideal gas equation?
PV = nRT
What does each letter stand for in the ideal gas equation?
- P-pressure
- V-volume
- n-no. of moles
- R-gas constant
- T-temperature
In the ideal gas equation what are the units for Pressure?
Pascals
In the ideal gas equation what are the units for Volume?
M³
In the ideal gas equation what are the units for Temperature?
Kelvin
How many Kelvin is 0°C?
273°K
