F4-C6- Salts, Acids and alkali Flashcards
What is an acid
A substance which dissolve and ionise in water to produce hydrogen ions.
All alkalis are bases. True or False?
True. Alkalis are bases which are soluble in water
Explain the reaction when ammonia is added into tetrachloromethane
- Ammonia can dissolve but cannot ionise in tetrachloromethane to form hydroxide ions.
- Ammonia exists as neutral covalent molecules in tetrachloromethane
- Ammonia cannot show its alkalinity without the presence of water.
- No effect towards red litmus paper
What is the colour of mthyl orange when in acidic, neutral and alkali condition?
acidic: red
neutral : orange
alkali : yellow
Define degree of ionisation of acids and alkalis
A measurement of the percentage of the total number of acid/ alkali molecules that will ionise when dissolved in water.
Explain phosphoric acid as a weak acid.
- Phosphoric acid dissolve and ionise partially in water to produce a low concentration of hydroxide ions.
- Most of the phosphocic acid still exists as covalent molecules and only a small number of the acid ionises to form hydrogen ions.
Why is totthpaste used to clean teeth?
- Totthpaste which is alkali can neutralise the lactic acid produced by bacteria in mouth
Name 2 examples of salts used in agriculture
- Fertilizers : ammonium sulphate, potassium chloride, ammonium nitrate
- Pesticides : copper (II) sulphate, iron(II) sulphate
What is the use of barium sulphate?
- used in medical field
- Patients drink before taking x-ray
NAme 2 examples of slats used is industry.
- Silver chloride/bromide to make photochromic glass
- Sodium carbonate to make soda lime glass
Is barium hydroxide soluble in water?
duhhh of coz
Is HgCl soluble in water?
noooh
Why does effervesence occur when mg powder added to aqueous hcl but no obersavtion is seen when mg powder is added to hcl dissolved in methylbenzene?
In aqeous HCL
- HCl dissolve and ionise in water to produce hydrogen ions and chloride ions.
- presence of hydrogen ions causes solution to be acidic
- Thus, HCL reacts with magnesium powder to produce hyrogen gas which causes effervescence
In HCL dissolved in methylbenzene
- HCl is a covalent compound
- HCl can dissolve but cannot ionise in methylbenzene to form hydrogen ions.
- No observation occurs because HCl cannot react with magnesium powder
During titration, why does the burette need to be rinsed with sulphuric acid after rising it with water.
ensure water droplets in the inner wall of the burette does not dilute the concentration of the acid used.
How to test for anion in potassium chloride solution
Anion: chloride ion
- add dilute HNO3
- add silver nitrate
- white precipitate forms indiciating prescence of chloride ions
in a solution,dilute hydrochloric acid and barium chloride is added. A white precipitate is formed indicating the presence of ______ anion
sulphate ion
How to test for presence of nitrate ion in salt solution?
dilute H2So4 + iron (II) sulphate + concentrated H2So4
- brown ring is formed
A colourless solution added with sodium hydroxide solution forms a white precipitate. In excess NaOh , it dissolves to form a colourless solution. What cation might be present
Zinc, aluminium, lead(II) ions
A colourless solution added with NH3 solution forms a white precipitate which remains incoluble in excess Nh3. What cation might be present?
Aluminium, Lead(II) or Magnesium ions
A solid is heated strongly and produces a brown gas with pungent smell. The residue is yellow when hot and white when cold. What inference can be made?
- Nitrogen dioxide gas is produced
- ZInc oxide is produced
When dilute HNO3 is added into a solution, bubbles of colourless gas are produced. The gas turns limewater milky indicating the presence of ___?
co2 gas
What is the use of Nessler reagent?
To comfirm the presence of Ammonium ion
When a solution is added with ammonia solution until in excess, what are the observations shown if copper (II) ion ins present?
- A blue precipitate is produced and dissolves in excess ammonia to form a dark blue solution
A BROWN solution is poured into a test tube and added with potassium thiocynate solution to determine the cation present. What observation and inference can be made?
- A blood red colouration is formed
- Iron (III) ions are present