Topic 4: Acids And Alkalis Flashcards
What is an aqueous solution?
A mixture that is formed when a substance is dissolved in water.
What is the difference between an acid and an alkali?
Acid: a solution that reacts with alkalis, turns litmus red and has a pH less than 7. They form H+ ions in water.
Alkali: a solution which contains excess OH- ions, turns litmus blue and has a pH greater than 7.
Define the term neutral:
A solution that is neutral has a pH of 7 and is turns green when universal indicator is added to it.
What are the problems with some acids and alkaline’s and how are these problems made aware to people?
They can be corrosive, toxic or harmful to the environment. The hazards associated with handling specific solutions are identified by international symbols. They indicate the precautions needed when handling them.
What is the pH scale?
This measure the acidity or alkalinity of a solution. The scale goes from 0-14. Above 7 means the greater the alkalinity of the solution. Below 7 means the stringer the acidity. 7 is neutral.
How can the pH of a solution be found?
Using indicators. Indicators are substances that change colour depending on the pH.
Why does universal indicator have a range of colours?
It is made from a mixture of different indicators and produces a range of colours depending on the pH.
What colours does litmus turn in the presence of an acid or an alkali?
Acid: red
Alkali:blue
What colours does methyl orange turn in the presence of an acid or an alkali?
Acid: red
Alkali: yellow
What colours does phenolphthalein turn in the presence of an acid or an alkali?
Acid: colourless
Alkali: pink
What is an ion and how does it form a positive or negative change?
An ion is an atoms that has become charged by loosing or gaining elections.
Losing electrons forms a positive charge because now there are more protons than electrons and haunting electrons forms a positive charge because there are now more electrons than protons.
What is a polyatomic ion and how is it formed?
They are formed when small groups of atoms held together by covalent bonds, lose or gain electrons. E.g OH-, NO3-, SO42-.
What do acids produce when the dissolve in water?
They produce an excess of hydrogen ions (H+) when they dissolve in water.
What to alkalis produce when they’re dissolved in water?
Excess hydroxide ions (OH-) in water.
What makes a concentrated acid solution?
The higher the number of hydrogen ions in a certain volume, the higher their concentration. The higher the concentration, the more acidic the solution and the lower the pH.
What makes a concentrated alkaline solution?
The higher the number of OH- ions (hydroxide ions) in a solution, the more alkaline the solution and the higher the pH.
Does a neutral solution contain hydrogen and hydroxide ions?
Neutral solution such as pure water have a pH of 7 and contain low equal concentrations of hydrogen ions and hydroxide ions.
What does the term ionise/dissociate mean?
Means the splitting up of a substance.
What is the difference between a concentrated solution and a dilute solution?
Concentrated solution: contains a lot of dissolved solute per unit volume.
Dilute solution: contains only a small amount of solute.
How can you work out the concentration of a solution in gdm3?
Concentration= amount dissolved (g)/volume of concentration(dm3)
1000cm3=1litre=1dm3
How does the pH scale show the difference in concentration of H+ ions?
Each time the pH scale increases by 1 the difference in concentration of H + ions multiply by 10. E.g:
A solution with a pH of 0 has a concentration of H+ ions that is 10,000 times greater than a solution with a pH of 4.
How does the concentration of a solution affect its rate of reaction?
The more concentrated a solution is (more acidic) the faster it reacts with substances.
What is a pH meter?
It is used to give more accurate measurements of the pH of a substance.
What is the difference between a string and weak acid?
Strong acids: their molecules dissociate completely into ions when they dissolve in water and produce a high concentration of hydrogen ions.
Weak acid: they do not dissociate completely into ions in solutions. Therefore they will only contain a few hydrogen ions as the rest have not dissociated.