chap 8: acids and bases Flashcards
what is an acid?
it is a substance that dissociates in water to produce hydrogen ions, H+
list 3 properties of acids
- sour taste
- produce ions when dissolved in water hence acids are able to conduct electricity (due to presence of mobile ions
- turns blue litmus paper red
what is the product of acid and reactive metals?
salt + hydrogen gas (H2)
how to check if an acid + metal reaction has taken place?
effervescence observed and metal dissolves
how to test for hydrogen gas?
use a lighted splint. in the presence of hydrogen gas, the lighted splint will extinguish with a ‘pop’ sound
what are some unreactive metals?
lead, copper, silver, gold
what are metals that are too reactive?
potassium, sodium, calcium
what is the product of acid + base
salt + water (H2O)
how to check if an acid reaction with base has occured?
solid base dissolves. resulting mixture feels warm to touch.
what is the reaction, where water is the only product other than salt?
neutralisation
what is the product of the reaction of acid with carbonates?
salt + carbon dioxide (CO2) + water (H2O)
how to check if an acid + carbonate reaction has taken place?
effervescence observed and metal carbonate dissolves
how to test for carbon dioxide gas?
bubble gas into limewater (calcium hydroxide). in the presence of carbon dioxide gas, white precipitate will be formed in the limewater. the white precipitate that forms is calcium carbonate.
what does the strength of an acid refer to?
strength of an acid refers to the extent of dissociation / ionisation of the acid when dissolved in water
what is a strong acid?
a strong acid is an acid that completely dissociates/ionises in water to give a high concentration of hydrogen (H+) ions.
what is a weak acid?
a weak acid is an acid that partially dissociates/ionises in water to give a low concentration of hydrogen (H+) ions
what does concentration refer to?
concentration refers to the amount of solute dissolved in 1 dm3 of water or solvent
what does basicity of acids refer to?
basicity of acids refer to the maximum number if hydrogen ions that can be produced by the ionisation of one molecule of the acid when dissolved in water
what is a base?
a base is any metal oxide or metal hydroxide. they contain either the oxide (O2-) or the hydroxide (OH-) ions
what are the characteristics of bases?
most bases are insoluble in water
bases react with acids in a neutralisation reaction to give salt and water only
what is an alkali?
an alkali is a soluble base that dissociates/ionises in water to produce hydroxide (OH-) ions
what is a strong alkali?
a strong alkali is an alkali that completely ionises /dissociates in water to give a high concentration of hydroxide (OH-) ions
what is a weak alkali?
a weak alkali is an alkali that partially ionises/dissociates in water to give a low concentration of hydroxide (OH-) ions
what are some properties of alkalis?
- bitter taste
-feel slippery and soapy
-produces ions when dissolved in water hence alkalis are able to conduct electricity (presence of mobile ions)
-turns red litmus paper blue
what are the products of an acid + alkali reaction
salt + water (H2O)
what are the products of an alkali +ammonium salt reaction?
salt + ammonia gas (NH3) + water (H2O)
how to check if an alkali + ammonia salt reaction has taken place?
effervescence observed and pungent gas produces
how to test for ammonia gas?
-use a piece of moist/damp red litmus paper
-if ammonia gas is released, the moist/damp red litmus paper turns blue
how does a pH scale work?
1-6: solution is acidic - concentration of H+ higher than concentration of OH-
7: solution is neutral - concentration of H+ ions equals to concentration of OH-
8-14: solution is alkaline - concentration of OH- higher than concentration of H+
what are the type of indicators to measure pH?
- methyl orange
-red colour in acidic solution
-changes colour from pH 3-5
-yellow colour in alkaline solution - screened methyl orange
-violet in acidic solution
-changes colour from pH 3-5
-green in alkaline solution - litmus
-red colour in acidic solution
-changes colour from pH 5-8
-blue colour in alkaline solution - thymolpthalein
-colourless in acidic solution
-changes colour from pH 9-10.5
-blue colour in alkaline solution - universal indicator
0-2: strong acid - red colour
3-6: weak acid - orange/yellow colour
7: neutral - green colour
8-10: weak alkali - blue colour
11-14: strong alkali - purple/violet colour
what nutrients do plants need to grow?
Nitrogen, Potassium and Phosphorus
what can cause the soil to be unsuitable for plant growth?
-too much fertiliser added
-environmental pollution such as acid rain
how is the pH of soil controlled?
chemicals are often added to the soil to adjust its pH. soil that is too acidic can be treated with bases such as slaked lime (calcium hydroxide). this process is known as “liming” the soil. adding too much slaked lime can result in the soil becoming too alkaline, which is unsuitable for plant growth ( cannot add sodium/potassium hydroxide —> too alkaline)
how are oxides classified?
- metallic oxides
-basic oxides
-amphoteric oxides - non-metallic oxides
-neutral oxides
-acidic oxides
what are basic oxides?
-all metal oxides (except ZAP oxides) are basic oxides
-most basic oxides are insoluble in water
-basic oxides are solids at room temperature
-they react with acids to form salt and water
what are amphoteric oxides?
-zinc, aluminium and lead (ii) oxide
-metallic oxides that react with both acids and bases to form salt and water
-can act as both a basic oxide and/or an acidic oxide
what are acidic oxides?
-most oxides of non-metals are acidic oxides
-most acidic oxides dissolve in water to form acids
- react with alkalis to form salt and water
what are neutral oxides?
-H2O (water), CO (carbon monoxide), NO (nitrogen monoxide)
-shows neither basic nor acidic properties
-insoluble in water
what are some strong acids?
HCl (hydrochloric acid), H2SO4 (sulfuric acid). HNO3 (nitric acid)
what are some weak acids?
H3PO4 (phosphoric acid), CH3COOH (ethanoic acid), H2CO3 (carbonic acid)
what are some weak acids?
H3PO4 (phosphoric acid), CH3COOH (ethanoic acid), H2CO3 (carbonic acid)
