Acids and Alkalis
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Why are hazard symbols useful?
They inform us of the dangers of a substance and indicate the precautions needed to be taken whilst handling them
What is the neutral pH
7 (below is acid and above is alkali)
How can the pH of a solution be found?
Using indicators that change colour depending on the pH
What is universal indicator
made of a mixture of different indicators and produces a range of colours depending on the pH
What colour do the following indicators turn in acid: litmus paper methyl orange phenolphthalein
red red colourless
what colour do the following indicators turn in alkaline: litmus paper methyl orange phenolphthalein
blue yellow pink
What is an ion and what has to happen in order for them to become positive or negative ions?
Ion is an atom that has become charged by losing or gaining electrons. Losing electrons make positive ions (cations) and gaining electrons make negative ions (anions)
What is a polyatomic ion?
Covalently bonded set of two or more atoms
How are polyatomic ions formed?
when small groups of atoms which are held together by covalent bonds, lose or gain electrons such as OH-
What do acids and alkalis produce when they are dissolved in water?
Acids-Hydrogen ions (H+) Alkalis-Hydroxide ions (OH-)
What does a high concentration of hydrogen or hydroxide ions mean?
It means that the concentration of the solution will be higher meaning that the pH will lower for acids and increase for alkalis. The solutions will become more acidic or alkaline.
What ions do neutral solutions contain?
low, equal amounts of hydrogen and hydroxide ions
What does a concentrated solution contain compared to a dilute solution?
concentrated- lots of dissolved solute dilute- not much dissolved solute
How do you calculate the concentration?
amount dissolved/volume of solution
What happens to the pH if the concentration of hydrogen ions is increased or decreased?
If the concentration of hydrogen ions increases by a factor of 10, the pH decreases by 1 and if the concentration of hydrogen ions decreases by a factor of 10, the pH increases by 1
What is the formula for sulfuric acid?
H2SO4
What is the formula for nitric acid?
HNO3
What is the alkali for NaOH
Sodium hydroxide
What is the formula for calcium hydroxide
Ca(OH)2
Give three strong acids
Nitric acid, hydrochloric acid, sulfuric acid
What happens to the molecules in strong acids
they dissociate (break up) into ions when they dissolve in water and produce high concentrations of hydrogen ions
Give an example of a weak acid and say why they are weak
Boric acid they do not dissolve completely into ions
What do the chemical properties of an acid depend on?
Its concentration and the type of acid
What is a base?
Substances that react with acids to form a salt and water only