Acids, Bases and Salts

Question 1

Colour of litmus in acid and alkali

Answer 1

Red in acid, blue in alkali

Question 2

Colour of phenolphthalein in acid and alkali

Answer 2

Colourless in acid, pink in alkali

Question 3

Colour of Methyl orange in acid and alkali

Answer 3

Red in acid, yellow in alkali

Question 4

Acid+Metal =

Answer 4

Salt+Hydrogen

Question 5

Magnesium reacts rapidly with dilute acids to form solutions of magnesium salts. What colour is the solution?

Answer 5

Colourless.

Question 6

Zinc reacts readily but not as much as magnesium because it is less reactive, what colour are zinc salts?

Answer 6

Colourless.

Question 7

Iron salts are…

Answer 7

Colourless.

Question 8

Acid+base…

Answer 8

Salt+Water

Question 9

Acid+metal carbonate…

Answer 9

Salt+Water+Carbon Dioxide

Question 10

Acid+Metal Hydgrogencarbonate…

Answer 10

Salt+Water+Carbon Dioxide

Question 11

Define an acid

Answer 11

Acids are substances which dissolve in water to form the H+ (aq) ion.

Question 12

Define a base

Answer 12

Bases are substances which react with acids i.e combine with H+ ions. Bases include metal oxides, metal carbonates and metal hydroxides.

Question 13

Define an alkali

Answer 13

Akalis are bases which dissolve in water to form the OH- (aq) ion. An alkali is a soluble base, all alkalis are bases but not all bases are alkalis.

Question 14

Define neutralisation

Answer 14

is a reaction of an acid with a base and it always results in the formation of a salt.

Question 15

When hydrogen burns what happens

Answer 15

Hydrogen oxide which is just H20 or water.

Question 16

Test to see if water is present

Answer 16

Cobalt chloride paper is used, it is blue when no water is present and turns pink when exposed to moisture.

Question 17

Test to show that water is pure

Answer 17

To show that a sample of water is pure, its boiling point can be measured. Pure water boils at 100 degrees, any impurities might change the boiling point.

Question 18

What compounds are soluble?

Answer 18

• All common nitrates
• All common sulfates
• All common chlorides
• All potassium, sodium and ammonium compounds are soluble
  
  • Sodium hydroxide, potassium hydroxide and ammonium hydroxide
  • Sodium carbonate, potassium carbonate and ammonium carbonate

Question 19

Which compounds are insoluble?

Answer 19

• All common carbonates
• All common hydroxides
• Calcium sulfate, barium sulfate and lead sulfate
• Silver chloride and lead chloride

Question 20

What solubility of salt do you prepare in precipitation?

Answer 20

• Insoluble

Question 21

How do you form an inoluble salt from a precipitation?

Answer 21

• Two solutons are mixed, each containing one of the two ions required to form the salt.
• On mixing these two ions combine and form the insoluble salt, which preciptates out of the solution, other ions are spectator ions.
• Preciptate is filtered off; washed, by pouring a little distilled water over the precipitate in the filter paper; then left to dry.

Question 22

How do you make barium sulfate?

Answer 22

• Insoluble salt so precipitation method
• Two solutions needed, one barium compoun and one sulfate compound.
  
  • Barium nitrate and sodium sulfate
• Two solutions are mixed, and the barium sulfate precipates out.
• Filtered washed and dried.

Question 23

What solubility of salt do yu prepare in titration?

Answer 23

• Soluble

Question 24

What two types of solutions do you sue in a titration?

Answer 24

• Acid and soluble base (alkali)

Question 25

What general salts are prepared using titration?

Answer 25

• Sodium, potassium and ammonium salts

Question 26

How do you prepare a soluble solt from titration?

Answer 26

• A known volume (usually 25cm³) of acid is measured in conical flask, using pipette.
• Few drops of indicator, such as phenolphathalein are added.
• Alkali placed in a burette and slowly added to conical flask.
• Whe indicator changes colour, with phenolphathalein, purple then the volume of alkali that has been added is recorded.
• Process repeated, to obtain a an accurate, average value.
• Once this exact volume is known, the process is repeated once more but without the indicator.
• Then warm the solution in a evaporating basin.
• Boil off half of the water to concentrate the soluton, then let the remainder cool and evaporate slowly to form large crystals.

Question 27

How do you make sodium chloride?

Answer 27

• It is soluble, so made by titration
• To make chlorine salte, hydrochloric acid must be used.
• To make sodium chloride we use sodium hydroxide.

Question 28

What four methods could be used to determine the end point of a titration reaction?

Answer 28

1. Use an indicator.
2. Use a pH meter.
3. Measure the conductivity of the solution.
4. Measure the amount of heat released into the solution.

Question 29

What solubilty of slat is prepared in a reaction of an acid with an insoluble base?

Answer 29

• Used to prepare soluble salt from an insoluble base

Question 30

How do you do a reaction of an acid and an insolubl base?

Answer 30

• Appropriate acid is placed in a beaker and warmed.
• Small portion of appropratie metal oxide or carbonate is added to warm acid and stirred.
• The oxide or carbonate reactions with the acid, forming a sosluble salt and appears to dissolve in the acid.
• More of the oxide or carbonte is added, a little at a time, with stirring.
• When acid has all been neutralsied the oxide or carbonate has nothing to react with and being insoluble sinks to the bottom.
• His can be filtered off, leaing pure salt solution.
• To obtain solid salt from solution, it is wamed gently in an evaporating basin and about half the water is boiled off to concentrate the osltuon.
• The remained is allowed to cool and to evaporate slowly forming large crystals

Question 31

How do you make copper(II) sulfate?

Answer 31

• To make sulfate salt, sulfric acid must be used
• Copper (II) sulfate is soluble, so precipitation cannot be used.
• Copper (II) hydroxide is insoluble, so titration cannot be used.
• So reaction of an acid with an insoluble base is used.