Acids and Bases (Chem) Flashcards
What is an acid?
An acid is a substance, a proton donor, that produces hydrogen ions when dissolved in water
Hydrochloric acid formula:
HCL
Nitric acid formula:
HNO3
Sulfuric acid formula
H2SO4
Ethanoic acid formula
CH3COOH
Properties of acids:
- sour taste
- conduct electricity (due to the mobile ions produced when dissolved in water)
- turn blue litmus paper red
acid + metal –>
salt + hydrogen
acid + base –>
Salt + water
acid + carbonate –>
salt + water + carbon dioxide
Difference between strong/weak acids
- strong acids ionise completely in aqueous solutions
- weak acids ionise partially in aqueous solutions
What does it mean by “strength of acid”
refers to the extent of ionisation of the acid in aqueous solution.
(The smaller the extent of ionisation, the weaker the acid)
What is an alkali?
It is a soluble base that produces hydroxide ions when dissolved in water
Properties of alkalis:
- bitter taste
- feel soapy
- conduct electricity (due to the mobile ions produced when they dissolve in water)
- turn red litmus paper blue
alkali + acid –>
salt + water
what is the reaction between alkali and acid called?
Neutralisation
alkali + ammonium salt –>
salt + water + ammonia
What does it mean by acidity?
Acidity depends on the concentration of hydrogen ions relative to that of hydroxide ions in a solution
What does it mean by alkalinity?
Alkalinity depends on the concentration of hydroxide ions relative to that of hydrogen ions in a solution
What is the purpose of PH scale?
It is used to indicate the acidity and alkalinity of solutions
What does a universal indicator do?
It shows a variety of colours at different PH values
What is the colour of Methyl orange indicator when soaked in acid/alkaline?
acidic - red
alkaline - yellow
What is the colour of screened Methyl orange indicator when soaked in acid/alkaline?
acidic - violet
alkaline - green
What is the colour of bromothymol blue indicator when soaked in acid/alkaline?
acidic - yellow
alkaline - blue
Describe the importance of controlling PH of soil
Soil of appropriate pH provides sufficient amounts of the required nutrients to plants. (usually suitable between ph 5-7)
Explain why soil becomes more acidic overtime
due to different environment conditions, such as acid rain
State what can be added to soil when it becomes too acidic
Bases, such as calcium hydroxide, can be added to soil that is too acidic.
Explain the process of liming and how it could controlled
During liming, the base reacts with the acids present in the soil to raise the pH of the soil.
To ensure that the right amount of base is added to soil, the pH of soil should be measured before and during the process of liming
What is precipitation and how does it work?
It is a method of preparing an insoluble salt in water.
It is the reaction between one reactant containing the cation of the salt and another reactant containing the anion of the salt
- soluble salt + soluble salt –> insoluble salt
- acid + soluble salt –> insoluble salt
Method steps:
1 Mix soluble salt and the other soluble salt in the beaker
2 filter to collect the precipitate of the desired insoluble salt as3 residue
4 Wash the precipitate with cold distilled water to remove impurities
5 Dry the precipitate between a few sheets of filter paper
What is titration and how does it work?
It is a method of preparing soluble salt in water
It is the reaction between an acid + (alkali or soluble carbonate) or anything that contains (grp 1 metal or ammonium)
