Separate chemistry Flashcards
What are the properties of transition metals
- High melting point due to electrostatic forces between positive metal ions and sea of electrons
- High density
- Form coloured compounds
- Useful as catalysts
What causes corrosion
Water and oxygen
How does sacrificial protection prevent the rusting of metal
Using a more reactive metal to coat a less reactive metal causing it to corrode instead
How can water and oxygen be excluded (not able to affect) from a metal
- Painting
- Coating with plastic
- Using oil or grease
How does electroplating improve the appearance and/or the resistance to corrosion of metal objects
- Acts as a barrier to exclude oxygen and water
- Improves appearance if electroplating with an unreactive metal
Why does converting pure metals into alloys increase the strength of the product
Pure metals = have positive ions the same size and in a regular arrangement so layers easily side over each other
Alloy = have positive ions of different metals which have different sized ions so layers can’t slide as easily
Why is iron alloyed with other metals to produce alloy steels
So they can be designed to fit a specific use
What are low-carbon steels used for and why
Sheeting as they are malleable and easily shaped
What are high carbon steels used for and why
Cutting tools since they are hard
What is the alloy of chromium and nickel used for and why
Stainless steels (used for cutlery) as they are resistant to corrosion
How is aluminium useful for its property
has a low density therefore used for aircraft
How is copper useful for its property
Good electrical conductor therefore used in cables
How is gold useful for its property
Good resistance to corrosion therefore used in jewlery
How is magnalium (aluminium + magnesium) useful for its property
Low density therefore good for cars and planes
How is Brass (copper + zinc) useful for its property
Hard and resistant to corrosion therefore used in coins
How do you work out concentration of a solution (2 ways)
- concentration (g/dm^3) = mass (g) ÷ volume (dm^3)
- concentration (mol dm^-3) = number of moles ÷ volume of solution (dm^3)
What are the two ways of showing concentration
g/dm3 or mol/dm3
How do you convert g/dm3 to mol/dm3
divide by the relative formula mass/molar mass
How do you convert from mol/dm3 to g/dm3
multiply by the relative formula mass
How do you convert a cubic centimetre into a cubic decimetre
divide by 1000
How do you convert a cubic decimetre into a cubic centimetre
multiply by 1000
How do you carry out an acid-alkaline practical
- add acid to burette using a funnel, record the volume in the burette to
start - add known volume of alkali to a conical flask and add some indicator
- place conical flask on white tile (so you can see colour change clearly)
- add acid to alkali and swirl until you reach the end point
- calculate how much acid has been added (titre)
- repeat until you get concordant titres
How do you work out percentage yield
(actual yield / theoretical yield) x 100
What are some causes for the actual yield being smaller than theoretical yield
- incomplete reactions
- side reactions
- reversibile reaction
What is atom economy
Amount of useful products gained from the reactances
How do you work out atom economy
atom economy = (Mr of desired product from reaction / sum of Mr of all reactants) x 100
Explain why a particular reaction pathway is chosen to produce a specified product
To produce a:
* a high atom economy
* a high yield
* at faster rate
What is molar volume in cm^3 and dm^3)
cm^3 = 24,000
dm^3 = 24
How do you calculate the volume of a gas
Volume = amount in mol × molar volume
What is Avogadro’s law
One mole of a substance contains 6.02 x 10^23 particles
How is equilibrium achieved at a faster rate
- Higher temperature is used
- A higher pressure
- A higher concentration is used
- A catalyst is used
How does temperature affect equilibrium
Increase of temperature: equilibrium will shift to favour the reaction which will reduce the temperature. (endothermic)
Decrease of temperature: equilibrium will shift to favour the reaction which will increase the temperature. (exothermic)
How does pressure affect equilibrium
Increase of pressure: reaction favours the side with a smaller molar volume
Decrease of pressure: reaction favours the side with a larger molar volume
What 3 compounds are used in fertilisers to increase agriculture
- Nitrogen
- Phosphorus
- Potassium
How does ammonia react with nitric acid to produce a salt that is
used as a fertiliser
ammonia + nitric acid → ammonium nitrate
(NH3 + HNO3 → NH4NO3)
What is the equation for forming ammonium nitrate
(NH3 + HNO3 → NH4NO3)
Describe the process of making ammonia sulphate in a lab
- reactants: ammonia solution and dilute sulfuric acid (bought from
chemical manufacturers) - SMALL scale
- only involves a few stages (titration then crystallisation)
Describe the process of making ammonia sulphate in an industry
- Ammonia: natural gas, air, water
- Sulfuric acid: sulphur, air,
water - LARGE scale
○ Many stages required (need to make ammonia and sulfuric acid, react
accurate volumes then evaporate)
How does a catalyst affect equilibrium
- doesn’t shift the position of equilibrium
- allows the equilibrium to be established faster
- less heat is needed
what happens if you increase the concentration of a reactant?
increasing the concentration of a reactant system makes more products to balance it out
NA
NA
When do chemical reactions stop
Chemical reactions stop when one of the reactants has been used up
What is the reaction in a hydrogen fuel cell
Hydrogen + Oxygen → Water
2H2 + O2 → 2H2O
What are the positives of using fuel cells
- produce only water as a waste
- Keeps producing fuel if being supplied
What are the negatives of using fuel cells
- difficult to transport/store hydrogen so
aren’t suitable for portable devices - expensive to make
