Topic 8 - Acids, Bases and Salts Flashcards
What is a base?
Bases are proton (H+) acceptors.
Is a base soluble?
Bases can either be soluble or insoluble in water. A soluble base is an alkali.
What is an alkali?
Soluble bases are known as alkalis, which are substances that release hydroxide (OH-) ions in aqueous solutions.
Examples of alkalis?
Alkalis are typically metal hydroxides.
Examples of bases?
Bases are typically metal oxides and metal carbonates.
What is the pH scale?
The pH scale is used to measure a substance’s ability to donate or accept a proton (H+).
What is an acid?
Acids are proton (H+) donors.
Examples of acids?
Nitric acid, sulfuric acid, hydrochloric acid
What do acids form in water?
Acids form hydrogen (H+) ions when they dissolve in water.
What do bases form in water?
Bases form hydroxide (OH-) ions when they dissolve in water.
What pH is acidic?
<7
What pH is neutral?
7
What pH is basic?
> 7
What is a strong acid?
An acid with a high ability to donate H+ ions and fully ionises in water e.g. Hydrochloric Acid.
What is a weak acid?
An acid with a low ability to donate H+ ions that doesn’t fully ionise in water e.g. Ethanoic Acid.
What is a strong base?
A base with a high ability to accept H+ ions that fully ionises in aqueous solutions e.g. Sodium/Potassium Hydroxide.
What is a weak base?
A base with a low ability to accept H+ ions that doesn’t fully ionise in aqueous solutions e.g. Ammonia.
What is ionisation?
Ionisation is the forming of ions, usually when reacting with water.
What is a concentrated acid?
Concentrated acids have a high number of moles of H+ ions per unit volume.
What is a dilute acid?
Dilute acids have a low number of moles of H+ ions per unit volume.
What is a concentrated base?
Concentrated bases have a high number of moles of OH- ions per unit volume.
What is a dilute base?
Dilute bases have a low number of moles of OH- ions per unit volume.
What are indicators?
Substances that change colour when they are added to acidic or basic solutions e.g. Litmus Paper
What colour is Litmus Paper in acids?
Red
What colour is Litmus Paper in bases?
Blue
What colour is Litmus Paper in neutral?
Violet
What colour is Methyl Orange in acids?
Red
What colour is Methyl Orange in bases?
Yellow
What colour is Methyl Orange in neutral?
Yellow
What is the equation for the reaction between metals and acids?
Metal + Acid —> Salt + Hydrogen
What does hydrochloric acid become when it reacts with a metal?
A Metal Chloride.
What does sulfuric acid become when it reacts with a metal?
A Metal Sulfate.
What does nitric acid become when it reacts with a metal?
A Metal Nitrate.
What is the equation for the reaction between metal oxides and acids?
Acid + Metal Oxide —> Salt + Water
What is the equation for the reaction between metal hydroxides (alkalis) and acids?
Acid + Metal Hydroxide —> Salt + Water
What is the equation for the reaction between metal carbonates and acids?
Acid + Metal Carbonate —> Salt + Water + Carbon Dioxide
What is a neutralisation reaction?
When an acid and alkali react, yielding a salt and water.
What is the equation for the heated reaction between ammonium salts and bases?
Base + Ammonium Salt —> Salt + Ammonia + Water
What compound creates a colour change when it reacts?
Copper Sulfate
Separating Mixtures Practical - Step 1
Use a Bunsen burner to gently warm the acid.
Separating Mixtures Practical - Step 2
Add the insoluble solid (with stirring) until the reaction no longer happens.
Separating Mixtures Practical - Step 3
Filter the solution to remove the excess insoluble solid and leave a solution of the salt dissolved in water.
Separating Mixtures Practical - Step 4
Heat the solution in an evaporating basin above a beaker of water. The ‘water bath’ ensures gentle heating.
Separating Mixtures Practical - Step 5
Let the solution cool and allow more water to evaporate. As water evaporates, the solution will become more concentrated and the salt will begin to crystallise.
What is universal indicator?
The indicator changes to a particular colour depending on the pH of a solution.
What is a pH probe?
The probe returns a number that represents the pH of a solution.
Specifically, what is the pH scale a measure of?
The numerical pH scale is a measure of the concentration of H+ ions in a solution. For every increase of 1 in pH, the concentration of H+ ions gets divided by 10.
What is the ionic equation for a neutralisation reaction?
H+(aq) + OH-(aq) —> H2O(l)
What is titration?
Titration is a technique that measures the volumes of acid and base solutions that are needed in a neutralisation reaction.
What are the variables of titration?
The concentration of the acid to be added and the volume of the base.
What colour is Phenolphthalein in acids?
Colourless
What colour is Phenolphthalein in bases?
Pink
Which point of neutralisation reactions do titration indicators help us see?
End-point
In titration calculations, what unit is concentration measured in?
Moles/dm3
In titration calculations, what unit is volume measured in?
Dm3
What is the equation to find concentration?
Number of moles/Volume
What is the equation to find the number of moles?
Concentration x Volume
What is the equation to find volume?
Number of moles/Concentration
1 dm3 is equal to how many cm3?
1000
Titration Calculations - Step 1
Write down the balanced symbol equation of the equation. Work out the ratio of reactants.
Titration Calculations - Step 2
Divide the volume by 1000 if it’s in cm3. Then, work out how many moles of the known substance you have using the formula n=cV.
Titration Calculations - Step 3
The number of moles for either substance follows the ratio found in Step 1. Complete any calculations necessary.
Titration Calculations - Step 4
Work out the concentration/volume of the “unknown” substance using the equation c=n/V or V=n/c .
What can be seen when a metal carbonate and an acid react?
Effervescence
Which compound is used to test for sulfates?
Barium Chloride
How can you test for sulfates?
Add Barium Chloride. If a white precipitate of Barium Sulfate is seen then a displacement reaction has happened.
How do you separate a sulfate test?
Filter through filter paper, wash with distilled water and dry.