Chapter 8 Flashcards
What type of reaction is to group 2 elements undergo
Group 2 elements undergo redox reactions with oxygen water and Dilute acids to form 2+ ions
Show the reaction between a group 2 elements and oxygen
Eg
2Mg + 02 -> 2MgO
Show the reaction between a group 2 elements and water
Should form hydroxide and hydrogen eg
Sr + 2H2O -> Sr(OH)2 +H2
Show the reaction between a group 2 elements and dilute acid
Group 2 elements and a diary acid should form a salt and hydrogen gas e.g.
Mg +2HCl -> MgCl2 + H2
What is the trend in reactivity down group two
Reactivity increases down group to because the ionisation energy decreases down the group due to the decrease in attraction between outer electrons and the nucleus due to increasing atomic radius and increased shielding
What are the reactions of group two oxides
Group to oxide reacts with water to form metal hydroxide which dissolve
Why did the group 2 oxides form more alkaline solutions as you go down the group
Due to the solubility of hydroxides in water increasing down group to
State some uses and the equations of group two as bases
Calcium hydroxide is used to neutralise acidic soils
Ca(OH)2 +2H+ —> Ca2+ +2H2O
Magnesium hydroxide and calcium carbonate are used as indigestion tablets
Magnesium hydroxide and calcium carbonate are used as indigestion tablets
Mg(OH)2 + 2HCl -> MgCl + 2H2O
What is the trend in boiling point of group 7
Boiling point increases as you move down the group as more electrons increase strength of London forces which increases energy required to break the forces which increases boiling point
What type of reaction is to group 7 participate in
Halogen atoms react by getting an electron to form a 1+ ion in a redox reaction
What is the reactivity trend down group 7
Reactivity decreases down the group 7 because atomic radius increases so shielding increases and there is less nuclear attraction to capture an electron from another species
How do you prove the reactivity trend down group 7
The change in Hawridge and reactivity can be seen in the halogen highlight displacement reaction reaction takes place the solution will change colour it is clear chlorine is the most reactive as it will not displace The change in Hawridge and reactivity can be seen in the halogen highlight displacement reaction reaction takes place the solution will change colour it is clear chlorine is the most reactive as it will not be displaced by bromine and iodine and I’ll be in the least reactive as it will be displaced by both chlorine and bromine
What is disproportionation
Disproportionation is a redox reaction in which the same element is both oxidised and reduced
So the reaction between chlorine and water
Chlorine and water undergoes disproportionation to form chloric and hydrochloric acid
Which is used in water treatment
Cl + H2O —> HClO + HCl
Show the reaction between chlorine and cold dilute Aqueous sodium hydroxide
Chlorine gas and coal die loot sodium hydroxide make sodium chlorate solution Which is used in bleach
Cl2 + 2NaOH —> NaClO + NaCl +H2O
What are the advantage Jews and disadvantages of using chlorine in water treatment
The advantages are that it kills disease-causing microorganisms and prevents algae growth
The disadvantages are it is a Respiratory Irritant chlorine can react with organic compounds in water to form chlorinated hydrocarbons which are linked to cancer
What are the alternatives to using chlorine in the water treatment
Ozone kills microorganisms but is expensive and has a short half life so does not purify the water for long
UV light kills microorganisms that is ineffective in cloudy water
Explain how to carry out the carbonate test
Absolute hydrochloric acid to the solution is it bubbles it could be a carbonate so double the gas 39 water which will turn milky if it is co2
Explain how to carry out the sulphate test
Add barium nitrate and precipitate will form if a sulphate was present
Explain how to carry out the halide test
Add aqueous silver nitrate to aqueous solution of a halide, a precipitating form white for chlorine cream for bromine and yellow iodine add aqueous ammonia to tell them apart as silver chloride is soluble in dilute and NH3 silver bromine is soluble in concentrated and 83 and silver iodide in soluble in both
Why does the carbonate test come before the sulphate test come before the halide test
Carbonate comes first as neither sulphate or halide ions produce bubbles with dilute acid
Sulphate comes next as carbonate will form a precipitate when barium nitrate is added
Halide tests have to be lost as both carbonate and sulphates will form the precipitate with silver nitrate
