Chemistry 3a Summary Questions Flashcards
Before 1800, how were elements classified?
By their relative atomic mass.
Give two reasons why Newlands’ Octaves was criticised.
1) he didn’t leave gaps for undiscovered elements
2) He didn’t have any evidence
3) he put metals and non-metals together
Why did Mendeleev leave gaps in his Table of Elements?
For undiscovered elements.
What does the group number mean?
How many electrons there are in the outer shell.
What is shielding?
Inner electrons getting in the way of the nuclear charge from the nucleus.
As you go down group one, what is the trend in reactivity?
As you go down group one the elements get more reactive.
What is the density of alkali metals?
The first three are less dense than water so will float.
What is the charge of a halide ion when it forms an ionic compound?
Negative.
What are the properties of a transition metal?
1) good conductors of heat and electricity
2) dense, strong and shiny
3) less reactive than group 1 metals
4) higher melting points than group 1 metals
What are the main ions that cause water hardness?
1) calcium ions
2) magnesium ions
What are two possible health benefits of drinking hard water?
1) good for teeth and bones
2) reduced risk of heat disease
What are two methods of removing permanent hardness from water?
1) running the water through an ion exchange column
2) adding washing soda (sodium carbonate)
During water treatment, how are microbes killed so that the water is safe?
Chlorine is added to the water to kill any microbes. Chemicals are added to make microbes join together.
Why isn’t tap water purified by distillation?
It is too expensive.
Why is flouride added to some drinking water?
It helps prevent tooth decay.
What is a reversible reaction?
A reversible reaction is one where the products if the reaction can themselves react to produce the original reactants.
What is meant by an equilibrium?
Where the mass of products and reactants remain constant, the forward reaction rate is balanced by the backwards rate.
How does changing the temperature and pressure of a reversible reaction alter the equilibrium position?
TEMPERATURE:
- increase = favours the endothermic reaction
- decrease = favours the exothermic reaction
PRESSURE:
- increase = encourage the reaction that produces less volume
- decrease = encourage the reaction that produces more volume
What effect does the iron catalyst have on the reaction between nitrogen and hydrogen? (The Haber process to make ammonia)
It increases the rate of reaction so the temperature can be as low as possible to get a high yield, but not too slow.
When alcohols dissolve in water, is the solution acid, neutral or alkali?
Neutral.
What is the functional group in carboxylic acids?
-COOH.
What are two uses of carboxylic acids?
1) ethanoic acid (in vinegar)
2) soaps and detergents
What two substances react together to form an ester and what is the catalyst that is used?
An ester is formed from an alcohol and a carboxylic acid reacting together, and the catalyst used is an acid (for example sulphuric acid).
What are two uses of esters?
1) perfumes
2) flavourings / aromas
3) ointments
4) solvents (for paint, ink, glue, nail varnish remover)
