Seperate Chemistry 1 Flashcards
What are the typical properties of transition metals?
High melting point
High density
Form coloured compounds
Transition metals and their compounds can be used as catalyst
Which transition metal in used in the haber process
Iron
What causes metal to corrode?
Oxygen reacts with the metal to form a metal oxide
Why is corrosion of a metal a redox reaction?
The metal loses electrons so is oxidised
Oxygen gains electrons so is reduced
What is rusting?
Rusting is the name specifically given to the corrosion of iron when it reacts to oxygen and water in the air.
What two substances need to be excluded to prevent rusting?
Oxygen (O2)
Water (H2O)
How can oxygen and water be excluded to prevent iron rusting?
Pain the metal
Coat the metal in oil/grease
Cover the metal in plastic
Keep the metal in a vacuum container
What is sacrificial protection? How does it prevent corrosion?
Sacrificial protection is when the metal being protected from rusting is galvanised with a more reactive metal.
The outer metal will corrode first and will prevent the corrosion of the inner metal
Which metal is used to in the sacrificial protection of iron?
Zinc
What is electroplating?
A process in which a metal coated with a layer of another metal.
What are two reasons for using electroplating?
To make a metal more resistant to corrosion
To improve the appearance of a metal. (Silver plated cutlery)
Explain how the process of electroplating works?
The metal being coated is the cathode. The metal that will form the exterior layer is the anode. The electrolyte solution must contain ions of the metal which will form the outer coating. A power supply is connected to both electrodes.
Why are pure metals generally very malleable?
The atoms lie in uniform rows which are able to Slide Over on another. As they are the same size.
What is an alloy?
An alloy is a mixture of two or more metals or a metal and another element.
A pure metal can be converted into an alloy. How does this increase the strength of the product?
Alloys contained several metals which will have different sized atoms. This distorted the regular arrangement of the atoms so they layers are unable to Slide Over one another very easily.
Why is iron alloyed with other metals to produce alloy steels?
Iron + Carbon = steel
Iron is relatively brittle so it is combined with other elements such as carbon produced a material more desirable qualities.
Low carbon steel: malleable so used for sheeting
High carbon: hard so used for cutting tools
Stainless steel: corrosion resistant so used for cutlery
What property of copper makes it suitable to be used in electrical cables?
Very good electrical conductor
What property of aluminium makes it suitable for use in aircrafts?
Low density
What is a key property of gold that makes it suitable for use in jewellery?
Very unreactive so resistant to corrosion
Jewellery appearance will not be affected over time.
What is magnalium? What is it used for?
Magnalium is an alloy of magnesium and aluminium.
It is lighter and stronger than aluminium and more resistant to corrosion. It is used for car and aircrafts.
What is brass? What is it used for?
Brass in an alloy of copper and zinc
Brass is hard and resistant to corrosion. It used for decorative hardware such as plumbing fittings.
How do you calculate the concentration of a solution in mol dm-3?
Moles / volume (dm3)
How do you convert from g dm-3 to mol dm-3?
Describe how to carry out an acid-alkali titration to find the concentration of alkali
1) Rinse the pipettes with the solution of unknown concentration (alkali) use this pipette to add a known volume of alkali to a conical flask
2) add few drops of indicator
3) rinse and fill the burette with acid
4) gradually add the acid to the conical flask
5) record the volume in the burette when the indicator changes the colour
6) repeat the experiment until you have concordant results
7) use results to calculate a mean titre and the concentration of alkali.
Calculate the number of moles of the alkali using known volume and concentration (moles = concentration x volume)
Use the chemical equation to work out the ratio of acid and alkali
Divide the moles of acid by the volume used in neutralisation to find concentration.
What is meant by the term theoretical yield?
The amount of product that would be collected under perfect reaction conditions.
How do you calculate percentage yield?
Percentage yield = (actual yield / theoretical yield) x 100
Why is the actual yield of the product be less than expected?
Incomplete reaction
Completing, unwanted side reactions
Practical loses/human error
What is atom economy of a reaction
A measure of the efficiency of the reaction. It looks at the amount of reactants that get turned into useful products.
How can atom economy be calculated
Atom economy = (Mr of desired / Mr reactants)x 100
Why might one reaction pathway be chosen over another?
Higher atom economy Higher yield Faster rate Equilibrium position favours products more By-products are more useful/less harmful
What does Avogadro’s Law state about gas volumes?
At the same temperature and pressure equal amounts of gas will occupy the same volume
What is the molar volume of a gas?
The volume occupied by one mole of molecules of any gas at RTP (room temp and pressure)
24dm3
What is RTP?
20°C
1 atmosphere
Molar volume calculation:
Describe the steps that are carried out during the haber process
Reactants are obtained (hydrogen from natural gas, nitrogen from air)
The gases are compressed to 200atm and heated to 450°C before being pumped into a tank containing layers of catalytic iron beads
Ammonia forms
Ammonia and unreacted hydrogen and nitrogen pass into a cooling tank where ammonia is collected as a liquid
The unreacted hydrogen and nitrogen are recycled back into the tank.
How is the rate of attainment of equilibrium affected by temperature?
A higher temperature means equilibrium is reached quicker. This is because the reacting particles have more Kinect energy so there are more frequent successful collisions.
How is the rate of attainment of equilibrium affected by a catalyst?
Equilibrium is reached faster when a catalyst is used because the catalyst provides an alternative reaction pathway with a lower activation energy.
How is the rate of attainment of equilibrium affected by pressure?
Equilibrium is reached faster with a higher pressure. This is because there are more particles in the same volume (or the same number of particles in a smaller volume) so more collisions between reacting particles.
How is the rate of attainment of equilibrium affected by concentration?
Equilibrium is reached faster at a higher concentration. This is because there are more particles in the same volume so more collisions between the reacting particles.
Why are conditions used in the haber process a compromise?
A high temperature increased the rate of reaction however, it will favour the reverse reaction, decreasing the yield. A compromise of 450°C is used to obtain a sufficient rate and yield.
A high pressure speeds up rate and favours the forward reaction (increasing the yield). High pressures can be dangerous and require expensive machinery so a compromise of 200atm is used
Why is a catalyst used in the haber process?
To increase the rate of reaction so more product is produced within the same time frame
What factors should be considered before deciding the conditions for an industrial reaction?
Availability and cost of raw material
Energy requirements
Optimum temperature and pressure for high yield and fast rate of reaction
Need for a catalyst
What is the purpose of fertilisers?
To promote plant growth
What chemical compounds might fertiliser contain?
Nitrogen, phosphorus and potassium compounds
What compound are found in NPK fertilisers?
A combination of all there fertilisers compounds: nitrogen, phosphorus and potassium compounds.
Which parts of plant growth do the compounds nitrogen, potassium and phosphorus help with?
Nitrogen: healthy lives
Phosphorus: healthy roots
Potassium: growth and healthy fruit/flowers
Which ammonium salt is most commonly used in fertilisers?
Ammonium nitrate
How is the salt ammonium nitrate formed? Write a chemical equation for the reaction taking place
What is the chemical equation for the formation of ammonium sulfate from ammonia and sulfuric acid?
How can ammonium sulfate be prepared in a laboratory?
Titration between ammonia and sulfuric acid:
How can ammonium sulfate be produced on an industrial scale?
Raw materials obtained from the haber process (ammonia) and the contact process (sulfuric acid). A large reactor chamber is filled with ammonia gas. Sulfuric acid is sprayed into the chamber from above. Ammonia sulfate crystals are produced
Compare the laboratory method of producing ammonium sulfate with the industrial process
How is voltage produced from a chemical cell?
Two metals of different reactivities are placed in an electrolyte.
The more reactive metal released electrons, becoming positively charged. The electrons flow to the other electrode which becomes negatively charged. The difference in the ability of each electrode to release electrons causes a voltage to be produced.
When will chemical cell stop producing a voltage?
When one of the reactants has been used up.
What is a fuel cell?
A cell that continually produces a voltage as long as it is supplied with oxygen and a fuel (like hydrogen).
What is the only product of a hydrogen-oxygen fuel cell?
Water
How does a hydrogen-oxygen fuel cell work?
Hydrogen and oxygen are pumper through a porous electrodes. The electrolyte is often an acid such as phosphoric acid.
Hydrogen and oxygen react, producing electricity and water.
Write an equation for overall reaction that takes place in a hydrogen-oxygen fuel cell
What are the advantages of using fuel cells?
No pollution produced
Produced more energy than an alternative fuel like petrol
Continuous process as like as fuel is supplied.
What are the disadvantages of using fuel cells?
Materials used to make them are expensive.
High pressure tanks required to store oxygen and fuels like hydrogen.
Hydrogen is expensive and hard to store.
Efficiency is affected by temperature.
Number of Particle formula
6,02 x 10^23 x moles
