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How could you determine the acidity of household items? - Coggle Diagram
How could you determine the acidity of household items?
What is an acid?
An acid is a hydrogen-containing substance with particular properties such as neutralising alkalis, making it typically corrosive and sour-tasting
Different types of acids
Organic
Organic acids are considered to be weak acids which are obtained from organic materials such as plants and animals. They are mainly composed of carbon, hydrogen, and oxygen and they don't completely dissociate in water. A few examples are citric acid and acetic acid
Inorganic
Inorganic acids are generally referred to as strong acids and are derived from minerals, and one or more inorganic compound. When dissolved in water, all inorganic acids form hydrogen ions and the conjugate base ions. A few examples are sulfuric acid, hydrochloric acid, and nitric acid
Types of household items
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride and water and is most commonly found in the human stomach, breaking down food. This acid is used in fertilisers, dyes, and in the production of chlorides
Acetic acid
Acetic acid is a clear, organic acid with a strong vinegar-like smell. It can be found in soil, water, and all sorts of foods. Acetic acid has many uses including the production of plastics, dyes, and insecticides
Citric acid
Citric acid is commonly used as a food additive, cleaning agent, and nutritional supplement. It is naturally found in citrus fruits such as lemons and limes
Sulfuric acid
Sulfuric acid is a colourless, oily substance made from sulfur, oxygen, and water. It can be found in car batteries and is mainly used in the production of phosphate fertilisers
Carbonic acid (soft rinks)
Carbonic acid is a compound made from hydrogen, carbon, and oxygen and can be found in human blood and rainwater. It is typically used in the production of carbonated drinks.
Methods to determine acidity
Generally acids react with bases to neutralise the properties of each solution and produce salts. This reaction works by the hydrogen cation combining with the hydroxide anion of the base to form water.
Titration
A titration is a process of volumetric analysis where a solution of known concentration is used to determine the concentration of another solution.
To perform a titration, the solution of known concentration (titrant) is slowly added to the solution of unknown concentration via a burette until the reaction has reached endpoint. This is determined by a change in colour of an indicator in the substance with unknown concentration.
Titrations are an accurate process as the volumes can be precisely determined using standard laboratory equipment
Thermometric titration
Similarly to a normal titration, a thermometric titration is a form of volumetric analysis. However, in a thermometric titration, the titrant is added at a constant rate and the endpoint is determined by measuring the temperature of the solution
Colorimetric methods
These methods are based upon the properties of acid-base indicator dyes which change colour corresponding to different the different pHs of a solution
Indicator solutions
Thymol blue indicator
In an acidic solution the thymol blue indicator will change from red to yellow, whereas in an alkaline solution the indicator will change from yellow to blue
Universal indicator
When used, a change in colour to red indicates a strong acid. A change to purple indicates a a strong base and a change to a yellow-green colour indicates a neutral solution
Phenol red indicator
This is a water-soluble dye used to indicate the pH of a solution. A change from yellow to red signifies a pH of 6.6 to 8 and a change to a bright pink colour signifies a pH above 8.1
Methyl orange indicator
Once neutralisation has occurred, the colour of the solution will change from red to orange
Paper tests
Paper tests are done by dipping the different types of paper into a solution and observing its change in colour.
Litmus paper
Litmus paper only determines if the substance is acidic, alkaline, or neutral with no pH value.
A change in colour from blue to red signifies an acidic solution
A change in colour from red to blue signifies an alkaline substance
No change in colour signifies a neutral substance
pH paper
This type of paper will determine if a solution is acidic, alkaline, or neutral.
A pH of less than 3 with the colour red indicates a strong acid
A pH of 3-6 with the colour orange/yellow indicates a weak acid
A pH of 7 with the colour green indicates a neutral acid
A pH of 8-11 with the colour blue indicates a weak alkaline
A pH of more than 11 with the colour purple indicates a stong alkaline
Safety Risks
Chemicals:
Contact with or ingestion of chemicals can cause serious harm and could possibly lead to death. To prevent this, all protective equipment should be worn and all chemicals should be disposed of appropriately. If contact or ingestion does occur, the area should be rinsed with water and a medical practitioner should be contacted
Beakers & Flasks
Sharp glass from potential broken beakers or flasks pose a great safety risk of being cut and potentially infected by the toxic chemicals. To prevent this, all beakers and glass objects should be carefully held and transported, and should not be placed near the edge of a bench or table. In the case that someone is cut, the glass should gently be removed from the wound using sanitised tweezers and the wound should be cleaned with warm water and soap. Gauze should be applied to the cut with pressure and if bleeding persists, a medical practitioner should be called. All broken glass should be disposed of appropriately and into a separate bin
Potential Errors
Systematic
Due to being supplied with the base solution, it is unknown if the prepared base solution is exactly 0.1mol/L
The pipettes used do not properly hold the accurate amount of solution with unknown concentration and fluctuate between measurements
Random
Determining the end point of a titration can be difficult and may vary between each person
Factors affecting the acidity of a substance
The acidity of a substance can be affected/determined by it's chemical structure. Typically when the H-A bond is more polar, the levels of acidity will be higher/stronger. Additionally, the periodic trends of the substance such as electronegativity and atomic radius can affect the acidity.
What is a base?
A base is a substance which can neutralise an acid by reacting with hydrogen atoms. Bases are majorly minerals reacting with acids to form water and salts.
Different types of bases
Weak base
A base which does not completely dissociate in water.
Eg. ammonia
Superbase
A base that is considered extremely strong. The ions of a superbase will completely dissociate in an aqueous solution.
Eg. sodium amide
Neutral base
A neutral base is any base with a pH of 7 or higher.
Eg. table salt
Solid base
A solid base is most active when in solid form.
Eg. silicone dioxide
What does acidity mean?
The term "acidity" refers to the level of acid in a substance such as water or soil.