Chemistry 2b

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  • Created by: JennD
  • Created on: 28-10-16 10:52
What 4 things does rate of reaction depend on?
Temperature, surface area, catalyst and concerntration
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What 3 ways can be used to measure the rate of reaction?
Precipitation, volume of gas, mass at the beginning of the experiment vs mass at the end of the experiment
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State what a precipitation reaction is?
When you mix 2 solutions together causing the solution to turn cloudy. To measure this you can time in seconds the time taken for a cross underneath to disappear
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State how to measure a rate of reaction using mass?
Using a mass balance measure the volume of 2 solutions mixed together. The as bubbles of gas are released the reading drops. The quicker the mass takes to drop the quicker the reaction
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State how to measure a rate of reaction using the volume of gas given off?
Using a gas syringe measure in seconds the time taken for a certain volume of gas to be produced
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State the reaction between hydrochloric acid and marble chips?
Reaction the marble chunks and hydrochloric acid together and using a gas syringe time in seconds the time taken for a volume of gas to be produced. Repeat this experiment using the same volume of HCl and same mass of marble, but crunch to small bits
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How does surface area affect the rate of reaction?
Smaller pieces have a larger surface area so the particles around the solution have more area to work on cuasing more frequent collisions
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Describe the reaction between magnesium metal and dilute HCl
This reaction measure how concerntration affects the rate of reaction. Time the time taken for magnesium to react with HCl, but each time add more water to the HCl making it more dilute
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How does concerntration affect the rate of reaction?
The higher the concerntration the quicker the reaction as the paricles are closer together so will have more frequent collisions
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Describe the reaction between sodium thiosulfate and HCl
This is a precipitate reaction. When you react the two together the solution goes cloudy, but if you increase the starting temperature of the solutions the reaction occurs quicker
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How does temperature affect the rate of reaction?
The higher the starting temperature the quicker the rate of reaction as the particles have more energy so will move quicker and will have more frequent collisions
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Describe the reaction of the decompostition of hydrogen peroxide
This is a slow reaction, but when magnesium oxide catalyst is added oxygen gas is given off quicker. You measure the volume of gas produced by using a gas syringe
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How does catalyst affect the rate of reaction?
The better the catalyst the quicker the reaction
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Name some catalysts found in daily life?
Patato peel and blood
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What if the deffinition of activation energy?
The minimum energy needed to produce products
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What is the deffinition of a catalyst?
A catalyst is a substance which speeds up a reaction without being changed or used up in the reaction
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How are catalysts important in industrial reactions?
They save companies money as the plant doesn't need to operate for as long to produce the same amount of stuff. Also it can be used a lower temps minimising energy lost saving money. Also they are never destoryed so can be used again
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What are the disadvantages of using catalyst?
They are very expensive to buy and different reactions need different catalysts to make one product, which costs alot of money.You have to keep mixtures very clean as sulfur impurities can poison iron catalyst so you can not use them again
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The deffinition of an exothermic reaction
An exothermic reaction is one which transfers energy to the surroundings, usually in the form of hear and usually shown by a temperature rise
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State some exothermic reactions
Combustion, neutralisation reactions, oxidation reactions, hand warmers, self heating cans etc.
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The deffinition of a endothermic reaction
An enothermic reaction is one which takes in energy from thre surroundings usually in the form of heat and is usually shown by a fall in temperature
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State some endothermic reactions
sports injury pack, decomposition on calcium carbonate to make quicklime
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Are reversible reactions exothermic or endothermic?
They are both exothermic and endothermic
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How is hydrated copper sulfate to anhydrous copper sulfate and water a reversible reaction?
If you heat blue hydrate copper sulfate crystals you get white anhydrous copper sulfate power (an endothermic reaction) and if you add a couple of drops of water to this you get blue crystals again (an exothermic reaction)
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What numbers show an acid on the pH scale?
pH6-pH0
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What nunmbers show an alkali on the pH scale?
pH8-pH14
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What ions do acids have?
H+ ions in water
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What ions do alkalis have?
OH- ions in water
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complete the word equation: acid+base=
salt+water
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complete this symbol equation: H+ + OH-=
H2O (water)
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What does the state symbol s mean?
Solid
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What does the state symbol l mean?
Liquid
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What does the state symbol g mean?
Gas
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What does the state symbol aq mean?
Dissolved in water
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Complete this word equation: acid+metal=
Salt+Hydrogen
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Why does copper not react with dilute acids at all?
Becuase it is less reactive then hydrogen
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What test is used to see if hydrogen gas is present?
The squeaky-pop test
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What will make a reaction faster?
How high up in the reactivity series the metal is
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What salts does hydrochloric acid make?
Chloride salts
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What salts does sulfuric acid make?
Sulfide salts
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What salts does nitric acid make?
nitrate salts when neutralised, but when reacted with metals it produces nitrogen oxide instead
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Complete the word equation:acid+metal oxide=
Salt+water
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Complete the word equation:acid+metal hydroxide=
Salt+water
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What happens when amonia dissolved in an alkaline solution is reacted with nitric acid?
You get a neutral salt called ammonium nitrate
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Complete the word equation:Ammonia+nitric acid=
Ammonium nitrate (NO WATER THOUGH)
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What is ammonia nitrate used for?
Fertiliser as it contains nitrogen from the ammonia and nitric acid. Plants need nitrogen to produce protiens
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How do you make an insoluble salt using a metal or an insoluble base?
React the metal or insoluble solid with the acid and wait until the solid dissolves and excess solid floats to the bottom. Filter this out. To get pure solid salt crystals evaporate off water making the solution more concerntrated (crystallisation)
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How do you make soluble salts using an alkali?
You have exactly the right amount of alkali to neutralise the acid by using the indicator to see when the reaction finishes, but repeat this without using the indicator. Then evaporate off the water to crystallise the salt as normal
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Why can't you make soluble salts using an alkali with the same method as making it with a metal?
You can not tell whether the reaction has finished
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How can you make insoluble salts using a precipitaion reaction?
You pick 2 solutions that contain the ions you need. Once the salt has precipitated out, filter this, wash it out and dry it on filter paper
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How can this precipitation reaction be used to clean water?
It removes poisonous ions from drinking water and removes calcium and magnesium ions making the water 'hard'
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What electorlytes made of usually?
Molten or dissolved ionic sturctures
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What conducts the electricity through the electrolyte?
The free ions
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What happens to the ions as they move from the positive electrode to the negative electrode?
They gain or lose electrons making them become atoms or molecules and are released
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What 2 things does reduction involve?
Loss of oxygen and the gaining of electrons
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What 2 things does oxidiation involve?
Gain of oxygen and loss of electrons
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How is reduction involved in electrolysis?
Where the positive ions from the anode are attracted to the negative charge of the cathode
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How is oxidation involved in electrolysis?
The negative ions from the cathode being attracted to the anode
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How does electrolysis work?
There is a flow of electrons. Electrons are taken away from the positive electrode and are given to other ions at the negative electrode. As ions gain or lose electrons they become atoms or molecules and are released
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What is the umonic for reduction and oxidation
OIL RIG
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What happends at the cathode in electrolysis of lead bromide?
The positive electrode is attracted to the negative electrode. Reduction ocurs at the negative electrode. At the anode one lead ions accepts 2 electrons to become 1 lead ion
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What happens at the anode in electrolysis of lead bromide?
The negative ions are attracted to the postive anode. Oxidation occurs at the anode. At the anode 2 bromide ions lose one electrons each and bcome one bromine molecule
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What happens if there is more than two free ions in the electrolyte?
At the negative electrode if metal ions and H+ ions are present the metal ions will stay in the solution due to the metal being more reactive then hydrogen (the more reactive metal is keener to keep ahold of its ions)
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Why in the electrolysis of sodium chloride does sodium stay in the solution and the hydrogen goes towards the cathode instead?
The sodium is more reactive then hydrogen. Hydroxide ions from the water are left behind causing sodium hydroxide to be left in the solution
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What do you have to make sure happens with half-equations?
Both sides of the equation are equal. The electrons balance
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Balance: H+ + e- -- H
2H+ + 2e- -- H2
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What is chlorine used for?
Bleach. Bleach is used in pools in order to kill microorganisms
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What is sodium chlrodie used for?
Soap due to it being an alkali
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Why is a cryolite used in electrolysis of aluminium oxide?
Aluminium oxide has a boiling point of 2000 degrees C meaning it is expensive to extract. Cyrolites bring down the melting point to 900 degrees C making extraction cheaper
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What is used for the electrodes in electrolysis?
Carbon Graphite sticks
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In electrolysis of aluminium oxide, the aluminium goes to the cathode and the oxygen goes to the anode. What happens to the anode?
It slowly decompses away due to the oxygen reacting with the carbon forming carbon dioxide
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What is electroplating?
Where you use the surface of one metal to coat the surface of another metal
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What is at the postive anode in electroplating?
The metal you would like to coat
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What is at the negative cathode in electroplating?
The metal which will be doing the coating
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What is the electrolyte solution made from?
The metal that is doing the coating
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Why is electroplating useful?
Decoration- allows you to coat cheap metals with expensive metals making it look prettier. Conduction- objects can be coated with copper in order to make them good conductors due to free to move electrons
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Card 4

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State how to measure a rate of reaction using mass?

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Card 5

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