Module 3 Flashcards
(S)
Solid
(G)
Gas
(L)
Liquid
(Aq)
Aqueous solution
GFM
Grand formula mass
Formula for mass
m= Number of moles x GFM
Formula for number of moles
Mass in grams / GFM
Formula for GFM
Mass in grams/ no. of moles
How to calculate the mass of product from a given mass of reactant
- Calculate n, the number of moles, for the substance whose mass has been provided
- Usle the “mole ratio” from the balanced equation to connect the chemical whose mass has been provided with the chemical whose mass we are trying to determine
- Caluculate m, mass for unknown chemical
Example 1. What mass of MgO is produced from 5g of Mg?
2Mg + O2 -> 2MgO
n=m/ GFM
= 5/24.5
=0.2 moles
2 moles of Mg -> 2 moles of MgO
0.2 moles of Mg-> 0.2 moles of MgO
m= n x GFM
= 0.2 x 40.5
= 8.1g
Example. Calculate the mass of NaCl made from 710g of Cl2
2Na + Cl2 -> 2NaCl
n=m/ GFM
= 710/71
=10 moles
1 mole of Cl -> 2 moles of NaCl
10 moles of Cl ->20 moles of NaCl
m=n x GFM
= 20 x 58.5
= 1170g
The 4 signs of a reaction
- Gas produced
- Colour change
- Change in tempreature
- Percipation
Examples of everyday reations
Burning toast
Baking a cake
Digestion
What properties can change to alter a reaction
Add a catalyst
Increase tempreture
Increase surface area
Increase concentration
What is concentration
Concentration is a measure of how much solute is dissloved in a particular volume of solvent
What happens if there is high concentration
Higher concentration = higher chance of a sucessful collison
What happens If the temperature is is high in a reaction
The faster the reactants move and the greater the chance of a sucessful collison at high temperature
In order to react something what has to happen
Atoms have to collide
If there is more surface area what greater chance is there?
A greater chance of a sucessful collison
What type of catalysts are there?
Biological (enzymes) or chemical
What do chemial catalysts do?
~ speed up at reaction
~ lower tempreature of a reaction
~can be re-used
~ are chemically unchanged
How does a catalyst work
The reactants move close together on the catalyst surface and react. The reaction speeds up
Average rate equation
Average rate= change in quantity/ change in time
What is (mol l -1)
Moles per liter to measure the concentration
