acids, bases & salts

Question 1

what is an acid

Answer 1

substance which ionizes in water/aqueous solutions to give hydrogen ions

Question 2

what are organic acids

Answer 2

carbon containing

Question 3

what do pure acids exist as

Answer 3

simple covalent molecules

Question 4

what is the nature of a solution of hydrogen chloride dissolved in methylbenzene and why

Answer 4

neutral
in absence of water, hydrogen chloride exists as simple molecules, no hydrogen ions formed

Question 5

what is a strong acid

Answer 5

acid that completely ionises in water to give hydrogen ions

Question 6

what is a weak acid

Answer 6

acid that partially ionises in water to give hydrogen ions

Question 7

what does the concentration of a solution refer to

Answer 7

measure of how much solute has dissolved in 1dm^3 of the solution

Question 8

what does the basicity of an acid refer to

Answer 8

maximum no. of hydrogen ions produced by one molecule of the acid when the acid molecule ionises in water

Question 9

what are the monobasic acids

Answer 9

hydrochloric acid
nitric acid
ethanoic acid

Question 10

what are the dibasic acids

Answer 10

sulfuric acid
carbonic acid

Question 11

what are the tribasic acids

Answer 11

phosphoric acid

Question 12

what is the solubilty in water for all ammonium salts and salts of grp 1 metals

Answer 12

soluble

Question 13

what is the solubilty in water for all nitrate salts

Answer 13

soluble

Question 14

what is the solubilty in water for all sulfate salts

Answer 14

soluble
insoluble: BaSO4 CaSO4 PbSO4 Ag2SO4(sparingly soluble)

Question 15

what is the solubilty in water for all chloride salts

Answer 15

soluble
insoluble: AgCl PbCl2

Question 16

what is the solubilty in water for all carbonate salts

Answer 16

insoluble
soluble: (NH4)2CO3 and carbonate of grp 1 metals

Question 17

what is the solubilty in water for all metal oxides

Answer 17

insoluble
soluble: oxides of grp 1 metals
(CaO slightly soluble)

Question 18

what is the solubilty in water for all metal hydroxides

Answer 18

insoluble
soluble: hydroxides of grp 1 metals
(Ca(OH)2 is lightly soluble)

Question 19

state the order of the reactivity series

Answer 19

potassium
sodium
calcium
magnesium
aluminium
zinc
iron
lead
copper
silver
gold
platinum

Question 20

which metals react explosively with acids

Answer 20

potassium
sodium

Question 21

which metals react vigorously with acids

Answer 21

calcium
magnesium
aluminum

Question 22

which metals react mildly with acids

Answer 22

zinc
iron
lead

Question 23

why does lead appear to not react with HCL and H2SO4

Answer 23

initial reaction of lead with these dilute acids form a layer of insoluble PbCl2 or PbSO4 which coats around the metal and prevents further reaction between the metal and acid

Question 24

why is a white precipitate seen when carbon dioxide gas is passed into limewater

Answer 24

carbon dioxide (acidic gas) reacts with limewater (aqueous calcium hydroxide, an alkali) to give calcium carbonate, an insoluble salt which appears as white precipitate

Question 25

what is a base

Answer 25

substance that reacts with an acid to form salt and water only

Question 26

why is no effervescence observed in a reaction between a base and ammonium salt

Answer 26

ammonia is highly soluble in water

Question 27

why is warming required in a reaction between ammonium salt and a base

Answer 27

decrease the solubilty of ammonia, allowing gas to be released

Question 28

what is precipitation

Answer 28

chemical reaction that produces an insoluble solid, known as precipitate when two aqueous solutions are mixed

Question 29

write the word equation for the reaction for precipitation of insoluble metal hydroxide

Answer 29

metal salt solution + alkali --> insoluble metal hydroxide (precipitate) + salt

Question 30

define pH

Answer 30

measure of how acidic or alkaline a solution, based on the centration of hydrogen ions in the solutions

Question 31

what is an indicator

Answer 31

organic compound that changes colour based on pH of a solution

Question 32

what is the pH range at which litmus changes colour

Answer 32

5-8

Question 33

what is the universal indicator

Answer 33

mixture of dyes available as a solution or pH paper provides a wide range of coloours corresponding to different pH values

Question 34

how can a pH meter more accurately measure pH

Answer 34

allows continuous recording of rapid pH changes

Question 35

why is not advisable to add slaked lime (calcium hydroxide) and chemical fertiliser, ammonium nitrate, to the soil at the same time

Answer 35

Other than neutralising the soil, the slaked lime will react with ammonium nitrate to produce ammonia gas which will escape into the air result in the loss of nitrogen content from the fertiliser added to the soil