Bases are metal oxides and metal Hydroxides.
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A base is a a substance, that can accept H+ ions and therefore are proton acceptor.
- Copper(II) Oxide (CuO)
- Iron(III) Oxide (Fe2O3)
- Copper (II) Hydroxide (Cu(OH)2)
- Iron (III) Hydroxide (Fe2O3)
It reacts with an acid to give salt and water only.
Neutralization reaction occurs, when Acid and Base react to form Metal Salt and Water.
An Alkali is a base, that is soluble in water.
Lets see what happens when an alkali (Sodium Oxide) is added to water
Examples of Alkalis:
- Sodium Hydroxide (NaOH)
- Potassium Hydroxide (KOH)
- Calcium Hydroxide (Ca(OH)2
- Barium Hydroxide (Ba(OH)2
- Aqueous Ammonia (NH3)
- Alkalis have bitter taste and soapy feeling.
- Turn Red litmus papers Blue.
- Produce Hydroxide ions when dissolved in H2
- All alkalis can react with acids to form a salt and water. This reaction is called neutralization. In this reaction the hydrogen ions from the acid and the hydroxide ions from the alkali react to form water.
- Alkalis when heated with ammonium salts give off ammonia gas.
- Alkalis can react with a solution of one metal salt to give metal hydroxide and another metal salt. The general equation for this reaction is:
- The Metal OH appears as a precipitate if it is insoluble in water.
Strong Alkali is that, which completely ionizes in solution.
Weak Alkali is that, which partially ionizes in solution.
Ammonium Hydroxide (Ammonia gas dissolved in water).–
Distinguishing between weak and strong Alkali:
Stronger Alkali at the same concentration has higher pH.
At the same concentration, stronger alkali would be the best conductor of electricity.
Uses of Basis And Alkalis:
- Ammonium Solution:
- In window cleaning solution
- In fertilizers
- In neutralizing acidic soil.
- To make Iron, Concrete and Cement.
- In toothpaste to neutralize acid on teeth.
- In antacids, to relieve indigestion.
- In making soaps and detergents.
- Industrial – Cleaning detergents.
p H scale:
The p H scale is a set of numbers used to indicate whether a solution is acidic, neutral or alkaline.
p H Calculation:
Based on number of H ions and OH ions:
Strong Acids – Higher concentration of H ions.
Strong Alkalis – Higher concentration of OH ions.
Why is Soil pH important?
- It affects the growth and development of plants.
- Plants best grow when the soil is neutral or slightly acidic.
- Plants will not grow in soil that is too acidic.
- This can happen when too much fertilizer is added to the soil and due to acid rain.
Hence the pH value of soil should be between 5 and 9.
Controlling Acidity of Soil:
- Chemicals are often added when soil becomes too acidic.
- The soil is treated with bases such as:
Quick Lime (Calcium Oxide) CaO
Slaked Lime (Calcium Hydroxide) CaOH
Lime Stone (Calcium Carbonate) CaCO3
- The basis react with the acids in the soil and raise the p H so that plants can grow healthily.
However adding too much base will make soil too much alkaline – thus making soil unsuitable for crop growth.
Oxides are compounds containing Oxygen.
- Non Metals may form acidic oxides.
- Most acidic oxides dissolve in water to form acids.
- They do not react with acids but they react with alkalis to form a salt and water.
- The oxides of metal are basic oxides.
- Most Basic Oxides are insoluble in water.
- Those that are soluble are called alkalis ( Na2O)
- Solid at room temperature.
- React with acids to form a salt and water.
- No reaction with bases or alkalis.
- In soluble in bases.
- Metal Oxides that react with both acids and basis to form salt and water.
- Oxides that contain both the abilities of acids and alkalis.
- If atmospheric oxide is reacted with an acid it will show the properties of an alkali and a neutralization reaction occurs.
- If it is reacted with an alkali – will shows acidic properties – a neutralization reaction occurs.
- Showing reaction with both acids and base.
- Oxides of Aluminum (Al), Zinc(Zn) and Lead(Pb).
- Produce Salt and H2O when reacting with acid or alkali.
- Some Non – Metals form oxides, that show neither basic nor acidic properties.
- Insoluble in Water.
- Do not react with acids or basis.
- Carbon Monoxide (CO)
- Water (H2O)
- Nitric Oxide (NO)
- Hydrogen Per Oxide (H202)
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