C4 - Stoichiometry Flashcards
What is a mole? [1]
- An amount of a substance containing 6.02×10²³ particles
What is the formula that relates to number of moles, relative formula mass and mass?
- m=n×Mr
What is a limiting reactant? [1]
- A limiting reactant is the reactant that is used up first.
What does it mean for a reactant to be in excess? [2]
- It means that that the other reactant will run out first
+ At the end of the reaction, there will be some left
What is the formula that relates to the number of moles (n), molar gas volume (Vm) and volume (V)? [1]
- n=V÷Vm (n=V÷24 at room temp and pressure)
(number of moles = volume ÷ molar gas volume)
Define molar gas volume (Vm) [1]
- The molar gas volume is the volume a single mole of any gas takes up
What is the volume (V) of one mole of any gas (Mr) in room temperature and pressure [1]
- 24dm³
How many cubic centimetres (cm³) does one cubic decimetre (dm³) contain? [1]
- 1000 cm³
How many times do you need to multiply 1dm³ by to get one cm³? [1]
- 1000 times
Define relative atomic mass [1]
- The relative atomic mass is the ratio of the average mass of one atom of an element to one twelfth of the mass of an atom of carbon-12
Define relative molecular mass [1]
- The sum of the relative atomic masses
What is Avagadro’s number? [1]
- 6.02×10²³
What do the following state symbols stand for; s, l, g, aq? [4]
- s = solid
- l = liquid
- g = gas
- aq = aqueous
What are the units for concentration? [2]
- g/dm³
- mol/dm³
What are the steps for calculation reacting masses? [5]
- Identify the two substances in the equation
- Write n (number of moles), m (mass) and Mr (relative molecular mass) underneath each one and fill in what you know
- Calculate the number of moles for one of the substances
- Consider the stoichiometric ratios in the equation to calculate the number of moles of the other substance
- Work out the mass / volume of the substance in question
How do do mass (g) and number of moles relate to relative formula mass? [1]
- The mass (g) of one mole is equal to the relative formula mass of the substance
What is the trend regarding reactivity in group 1, and why? [4]
- Reactivity increases down the group
- Outer shell is farther away from the nucleus,
+ making the force of attraction weaker,
+ which makes it easier to lose the electron
What is the trend regarding reactivity in group 7, and why? [4]
- Reactivity decreases down the group
- Outer shell is farther away from nucleus,
+ making the force of attraction weaker,
+ which makes it harder to gain an electron
What are the trends in group 1 (alkali metals) regarding reactivity, density and melting point going down the group? [3]
- Reactivity increases
- Density increases
- Melting point decreases (softness increases)
What are the trends in group 7 (halogens) regarding reactivity, density, melting point and colour going down the group? [4]
- Reactivity decreases
- Density increases
- Melting point increases
- Colour becomes darker
