Chemistry 2b flashcards

  • Created by: Evie
  • Created on: 23-04-13 16:56
What 4 things does a rate of reaction depend on?
Temperature, concentrations (or pressure for gases), catalysts and the surface area of solids
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What is the equation for rates of reaction?
Amount of reactant used or product formed / time.
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How do you measure the rate of reaction by precipitation? What are some problems with this method?
Observe a mark through the solution and measure how long it takes to disappear. The result is subjective and the initial solution needs to be see-through.
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How do you measure the ROR by a change in mass? Pro and con?
Measuring the speed of a reaction that produces a gas can be carried out on a mass balance. The quicker the reading on the balance drops, the faster the reaction. Pro- most accurate method. Con- releases gas into the room.
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How do you measure the ROR by the volume of gas given off? Pro and con?
Use a gas syringe. The more gas given off in a time interval, the faster the reaction. Pro- quite accurate. Con - could blow plunger out of syringe if its too vigorous.
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Name and describe a reaction to demonstrate ROR/ surface area.
HCl and marble chips. Measure volume of gas evolved & take readings at regular time intervals. Repeat but crush up the marble chips more, then try with powdered chalk.
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Name and describe a reaction to demonstrate ROR/ concentration
Magnesium metal with dilute HCl. The reaction gives of hydrogen gas which we measure with a mass balance. You can repeat and make the HCl stronger/weaker.
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Name and describe a reaction to demonstrate ROR/temperature
HCl and sodium thiosulfate produce a cloudy precipitate. Both chemicals are clear but when they react they form a yellow precipitate of sulfur. Make a mark and time how long its visible for. Repeat at different temperatures.
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Name and describe a reaction to demonstrate ROR/ catalyst
The decomposition of hydrogen peroxide. Its normally quite slow but using a manganese oxide catalyst speeds it up. Oxygen is given off so use a gas syringe. Repeat with different catalysts/amounts of manganese oxide.
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What does collision theory state?
the ROR depends on how often and how hard the reacting particles collide with each other. The particles have to collide in order to react and they have to collide hard enough/with enough energy.
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Name/explain 3 factors that increase collisions
Higher temperature (move quicker), higher pressure/concentration (more particles to collide with), larger surface area (more area for particles to work on)
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Activation energy. DEFINE IT.
The minimum amount of energy needed by the particles to react
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What is an exothermic reaction? Give examples.
One which gives out energy to the surroundings (usually in the form of heat). Burning fuels/combustion, neutralisation reactions, oxidation.
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What is an endothermic reaction? Give examples.
One which takes in energy from the surroundings (usually in the form of heat). Thermal decomposition or sports injury packs.
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Give an example of an endo/exo reversible reaction. Which is which?
Hydrated copper sulfate (A)→ ← anhyrous copper sulfate + water (B). A-B endo. B-A exo.
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What ions to acids form? What is an alkali and what ions does it form?
Acid makes H+ ions in water. An alkali is a base that dissolves in water. They form OH- ions in water.
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What is a neutralisation reaction?
Acid + base → salt + water
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What is the reaction using metals and acid? Give an example.
Acid + metal → salt + hydrogen. Dilute acid and a metal make a big squeaky pop when you burn the hydrogen released.
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How do you make a soluble salt using a metal or an insoluble base? What is this method called?
Add a metal, metal oxide or hydroxide to the acid. The solid dissolves. Its finished when the excess solid sinks. Filter excess metal to get the salt solution. Evaporate some of the water then leave it to evaporate slowly. Crystallisation.
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How to you make a soluble salt using an alkali?
You add the exact amount of alkali to just neutralise the acid. Then use an indicator to show when its finished. Repeat using the same volumes of acids/alkalis so its not contaminated with indicator. Then crystallise it.
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How do you make an insoluble salt? Give an example.
Precipitation reaction. Pick 2 solutions that contain the ions. Once the salt has precipitated, filter is and wash it with distilled water and dry on filter paper. Lead nitrate solution with sodium chloride solution.
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What can precipitation reactions be used for?
Removing poisonous ions from drinking water or sewage.
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Define electrolysis.
When you pass an electric current through an ionic compound (thats molten or in a solution) and it breaks down into its elements.
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What is the liquid called which conducts the electricity in electrolysis?
Electrolyte.
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What is reduction and oxidation?
Reduction is a gain of electrons, oxidation is a loss of electrons (gain of oxygen)
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Explain the electrolysis of molten lead bromide?
+ions are attracted to the cathode, they gain electrons (reduction). 1 lead ion accepts 2 electrons = 1 lead atom. -ions are attracted to the anode, they lose electrons (oxidation). 2 bromide ions lose one electron each = one bromine molecule.
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Explain the electrolysis of sodium chloride solution?
At the cathode 2 hydrogen ions accept 2 electrons = 1 hydrogen molecule. At the anode 2 Cl- ions lose their electrons = 1 chlorine molecule. The sodium ions stay in the solution as they're more reactive than hydrogen. Leaving NaOH in the solution.
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Write out the half equations for sodium chloride solution.
Cathode= 2H+ + 2e- → H². Anode= 2Cl- -- 2e- → Cl²
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Write out the half equations for molten lead bromide.
Cathode= Pb²+ + 2e- → Pb. Anode= 2Br- -- 2e- → Pb²
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What are some useful products from the electrolysis of NaCl solution?
Chlorine can be used in the production of bleach and plastics. Sodium hydroxide is a strong alkali which can make soap.
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What does the electrolysis of NaCl produce?
Hydrogen, chlorine and sodium hydroxide.
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How do you prepare aluminium before electrolysis?
Its main ore is bauxite, after mining/purifying, a white powder is left. This is pure Aluminium oxide (Al²O ³).
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Explain the electrolysis of aluminium.
Instead of melting you dissolve it in molten cryolite. This brings the temp down, making it cheaper/easier. The electrodes are made of carbon, a good conductor. Al forms at the cathode, O2 forms at the anode, produces CO2 so they get eaten away.
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Write out the half equations for the electrolysis of aluminium.
Cathode= Al³+ + 3e- → Al. Anode= 2O²+ → O² + 4e-.
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Explain electroplating through electrolysis.
The cathode is the metal object you want to plate, the anode is the pure metal you want to coat with. The electrolyte must contain ions of the plating metal
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Uses for electroplating?
Decoration (cheaper). Conduction: plate metals for electronic circuits.
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Other cards in this set

Card 2

Front

What is the equation for rates of reaction?

Back

Amount of reactant used or product formed / time.

Card 3

Front

How do you measure the rate of reaction by precipitation? What are some problems with this method?

Back

Preview of the front of card 3

Card 4

Front

How do you measure the ROR by a change in mass? Pro and con?

Back

Preview of the front of card 4

Card 5

Front

How do you measure the ROR by the volume of gas given off? Pro and con?

Back

Preview of the front of card 5
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