Chemistry ESSENTIAL KNOWLEDGE

Created by

Reja Bilal

Cards (119)

What is activation energy?
The minimum amount of energy that particles need to react
Why is a polystyrene cup used in experiments?
It is an insulator, so it reduces heat loss
What is metallic bonding? 
The electrostatic attraction between positive charged ions and delocalised electrons.
What is ionic bonding? 
The electrostatic attraction between oppositely charged ions
What is covalent bonding?
The electrostatic forces of attraction between a shared pair of electrons and the nuclei of the bonded atoms
What is dynamic equilibrium?
Equilibrium in a closed system where reactions take place at the same time in both directions at an equal rate
What is thermal decomposition
the breaking down of a substance by heating
What is the chemical equation for thermal decomposition of copper carbonate
CuCO3 —> CuO + CO2
What is the colour change in thermal decomposition
Green to black
Why does a catalyst have no effect on yield
Catalyst increases rate of forward reaction and backwards reaction EQUALLY
What is the equation for enthalpy change
ΔH = energy of products - energy of reactants
What is enthalpy change?
The heat energy transferred in a reaction at constant pressure
If the temperature in a dynamic equilibrium reaction changes and the pressure remains unchanged, where does equilibrium shift to?
If temp INCREASES, moves to ENDOTHERMIC side
If temp DECREASES, moves to EXOTHERMIC side
If pressure changes but temperature stays the same in a dynamic equilibrium reaction, where does equilibrium shift to?
If pressure INCREASES, goes to side with LESS MOLES
If pressure DECREASES, goes to side with MORE MOLES
What factors affect rate of reaction (4 points)
- concentration (pressure if gas)
- temperature
- use of a catalyst
- surface area
How to do a flame test
Dip clean nichrome wire loop (dip in HCL first to clean) into substance and hold over roaring blue flame and record colour
What are the 5 elements you can test using a flame test and what are the colours they show
Lithium - RED
Sodium - YELLOW
Potassium - LILAC
Calcium - ORANGE-RED
Copper - BLUE-GREEN
What are the 3 elements that form a coloured precipitate when you add a specific hydroxide?
Add SODIUM HYDROXIDE:

Copper - LIGHT BLUE precipitate
Iron (II) - GREEN precipitate
Iron (III) - RED-BROWN precipitate
What is a chemical test for water
Turns anhydrous copper sulfate from WHITE to BLUE
How to test for ammonia
Turns damp red litmus paper BLUE
How to test for chlorine
Bleaches damp litmus paper
How to test for hydrogen gas
When a lighted splint is inserted, a squeaky pop sound is heard
How to test for oxygen
It will relight a glowing splint
How to test for carbonates
Add HCl to sample
CO2 gas will be produced and when bubbled through limewater it turns cloudy
How to test for chloride ions
Add dilute nitric acid and add aqueous silver nitrate
Forms WHITE precipitate
How to test for bromide ions?
Add dilute nitric acid and add aqueous silver nitrate
Forms CREAM precipitate
How to test for iodide ions?
Add dilute nitric acid and add aqueous silver nitrate
Forms YELLOW precipitate
How to test for sulfate ions?
Add dilute HCl and aqueous barium chloride
forms WHITE precipitate
What is an exothermic reaction?
A reaction where energy is transferred to the surroundings.
Shown by INCREASE in temperature
What is an endothermic reaction? 
A reaction that takes in energy from its surroundings
Shown by DECREASE in temperature
When ethanol is heated with acidified potassium dichromate, what does the ethanol oxidise to? What is the colour change?
Oxidised to ETHANOIC ACID
Potassium dichromate goes form ORANGE to GREEN
Describe how to do a titration (6 points)
1. Add 25cm3 of alkali into a conical flask
2. Place conical flask onto a white tile (to see colour change clearly) and attach a burette to a clamp stand
3. Add indicator into flask
4. Add acid drop by drop while continuously swirling (to mix all the reactants thoroughly) until you achieve a complete colour change
5. Record volume of acid by reading BELOW the meniscus
6. Repeat titration until you achieve concordant results (within + or - 0.2cm3 of each other)
Describe how to make pure, dry CRYSTALS from a solution (4 points)
1. Gently heat solution in evaporating basin
2. After point of crystallisation (when you see crystals start to form), remove dish from heat and leave solution to cool
3. Salt should form crystals
4. Filter crystals and then dry in oven or using paper towels
Describe how to make an insoluble salt, e.g. LEAD SULFATE (5 points)
PRECIPITATION REACTION:
1. Mix the 2 salt solutions together in a beaker to form a precipitate
2. Stir with glass rod
3. Filter using filter paper and funnel to collect precipitate
4. Wash with distilled water
5. Dry by leaving in oven to evaporate excess water
Describe how to make a soluble salt from an acid and an insoluble base, e.g. COPPER SULFATE (7 points)
1. Heat acid in beaker
2. Add base until in excess (no more solute dissolves) and stir with a glass rod
3. Filter the mixture using filter paper and funnel

4. Gently heat filtrate to evaporate some of the water
5. Until crystals form on glass rod, showing a HOT SATURATED SOLUTION has formed
6. Allow solution to cool so crystals form
7. Filter, wash and dry in oven
Describe an experiment to find rate of reaction
1. Add measured vol of HCL acid of known concentration in conical flask
2. Add known mass of CALCIUM CARBONATE as marble chips
3. Using gas syringe, measure volume of gas produced at regular time intervals
4. Repeat with same volume, conc., mass, but crunch marble chips to increase SURFACE AREA
How can a student can compare the reactivity of bromine and reactivity of chlorine
Add chlorine solution to potassium bromide. It should turn ORANGE because bromine is displaced, which shows that chlorine is more reactive than bromine
How can a student can compare the reactivity of iodine and reactivity of chlorine
Add chlorine solution to potassium iodide. It should turn BROWN because iodine is displaced, which shows that chlorine is more reactive than iodine
How can a student can compare the reactivity of iodine and reactivity of bromine
Add bromine solution to potassium iodide. It should turn BROWN because iodine is displaced, which shows that bromine is more reactive than iodine
Acid + metal oxide/hydroxide 
metal salt + water