Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to...
-
Upload
morris-hubbard -
Category
Documents
-
view
216 -
download
1
Transcript of Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to...
![Page 1: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/1.jpg)
Indicators and pH
![Page 2: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/2.jpg)
Most solutions of acids and alkalis are colourless.
How to tell if a solution is acidic or alkaline?
![Page 3: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/3.jpg)
An indicator is a substance that has different colours in acidic and alkaline solutions.
Common examples: Litmus Phenolphthalein Methyl Orange
![Page 4: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/4.jpg)
![Page 5: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/5.jpg)
Grown in acidic soil – they are blue.
Grown in alkaline soil – they are pink/red
![Page 6: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/6.jpg)
A set of numbers used to indicate whether a solution is acidic, neutral or alkaline.
A measure of the acidity or alkalinity of a solution is known as pH.
![Page 7: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/7.jpg)
The pH of a solution is calculated based on the concentration of H+ or OH- present in a solution.
More acidic More alkaline Neutral
![Page 8: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/8.jpg)
pH < 7: Acidic Contains H+
The smaller the pH, the more acidic the solution, the more H+ it contains
pH = 7: Neutral. This is the pH of pure water.
pH > 7: Alkaline Contains OH-
The greater the pH, the more alkaline the solution, the more OH- it contains
![Page 9: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/9.jpg)
Manufacturers have come up with lipsticks that change colour when you put it on. Many believe that the colour of the lipstick depends on the wearer’s mood.
The colour of the lipstick depends on the pH of our skin (which is affected by diet, stress and physical activity level)
![Page 10: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/10.jpg)
1. Universal Indicator A mixture of indicators Gives different colours at different pH values Approximate pH values
![Page 11: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/11.jpg)
2. pH meter Accurate pH values pH probe is dipped into solution and pH is
shown on the meter either on a scale or digitally
![Page 12: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/12.jpg)
3. pH sensor and computer A pH sensor connected to a computer through
an interface can be used to measure the pH of a solution
![Page 13: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/13.jpg)
pH and the body Substances in your body have different pH
values.▪ Stomach (pH ~1.5)▪ Small intestine (pH ~8.4)▪ Blood (pH ~7.4)
E.g. If the pH of the blood is changed by one unit during an injection, the person will die!
![Page 14: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/14.jpg)
pH and food preservation Fresh food go bad due to microorganisms (bacteria)
present. Microorganisms do not grow well in solutions of low
pH.
E.g. Acids can be used to preserve food. ▪ Ethanoic acid (vinegar)▪ Benzoic acid▪ Citric acid
![Page 15: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/15.jpg)
pH and hair Shampoos are alkaline – to dissolve
grease. Alkalis damage hair – we must
always rinse away shampoo after use.
Hair conditioners – contain weak acids, to restore pH of hair to its normal value (weakly acidic: pH ~5)
![Page 16: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/16.jpg)
pH and agriculture* The pH of the soil is important for good plant
growth. Most plants grow best when the pH of the soil
~5.6 (weakly acidic). Most plants will not grow well in soils that are
too acidic/alkaline.
![Page 17: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/17.jpg)
pH and agriculture* Soils become acidic from:
▪ Extensive use of chemical fertilisers▪ Acid rain
Excess acidity can be neutralised by adding calcium hydroxide (‘slaked lime’) – ‘liming the soil’.
![Page 18: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/18.jpg)
Bases are the oxides or hydroxides of metals. Contains either oxide ions (O2-) or hydroxide ions (OH-)
Base Formula Ions presentSodium oxide Na2O
Zinc oxide ZnO
Copper(II) oxide CuO
Magnesium hydroxide Mg(OH)2
Aluminium hydroxide Al(OH)3
Na+ ; O2-
Zn2+ ; O2-
Cu2+ ; O2-
Mg2+ ; OH-
Al3+ ; OH-
![Page 19: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/19.jpg)
![Page 20: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/20.jpg)
Oxides of non-metals (non-metal + oxygen) React with water to form acids React with alkalis to form salt and water
Acidic OxideAcidic Oxide FormulaFormula Acid Produced with WaterAcid Produced with Water
sulphur trioxide SO3 sulphuric acid, H2SO4
sulphur dioxide SO2 sulphurous acid, H2SO3
carbon dioxide CO2 carbonic acid, H2CO3
phosphorous(V) oxide
P4O10 phosphoric acid, H3PO4
![Page 21: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/21.jpg)
Oxides of metals (metal + oxygen) React with acids to form salt and water
Basic OxideBasic Oxide FormulaFormula
magnesium oxide MgO
sodium oxide Na2O
calcium oxide CaO
copper(II) oxide CuO
![Page 22: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/22.jpg)
Oxides of metals Behave as acidic oxide or basic oxide React with acids and alkalis to form salts
Amphoteric OxideAmphoteric Oxide FormulaFormula
aluminium oxide Al2O3
lead(II) oxide PbO
zinc oxide ZnO
![Page 23: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/23.jpg)
Do not react with acids or bases Do not form salts
Examples: Water, H2O Carbon monoxide, CO Nitrogen monoxide, NO
![Page 24: Acids and Bases (4) Indicators and pH. Most solutions of acids and alkalis are colourless. How to tell if a solution is acidic or alkaline?](https://reader030.fdocuments.net/reader030/viewer/2022032612/56649ec85503460f94bd5907/html5/thumbnails/24.jpg)