Which ions causes a substance to be acidic?
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Which ions causes a substance to be acidic?
The ion that causes a substance to be acidic is a hydrogen ion / H+.
Which ions causes a substance to be alkaline ?
The ion that causes a substance to be alkaline is a hydroxide ion / OH-.
What pH is classed as neutral?
pH 7 is classed as neutral.
What pH range is classed as alkaline?
The pH range for alkaline is 8-14.
What pH range is classed as acidic?
The pH range for an acid is 0-6.
What colour is litmus in acidic and alkaline conditions?
Litmus is red in acid and blue in alkaline conditions.
What colour is phenolphthalein when added to an acid?
Phenolphthalein is colourless in acid.
What colour is methyl orange in acidic and alkaline conditions?
Methyl orange is red in acid and yellow in alkaline conditions.
Describe how to use universal indicator to test the pH of a substance.
To measure the pH of a substance with universal indicator:
Add a few drops of universal indicator solution to the substance.
Check the colour against a colour chart to determine the pH value.
(Universal indicator paper can also be used).
Why is universal indicator not used measure pH during titrations?
Universal indicator is not used for titrations as it does not give a sharp colour change which is required to identify the end-point.
The pH scale starts at pH 0 and goes up to what pH?
The pH scale goes from pH 0 - 14.
True or False?
The higher the concentration of hydrogen ions in solution, the lower the pH.
True.
The higher the concentration of hydrogen ions, the lower the pH.
True or False?
The higher the concentration of hydroxide ions in solution, the higher the pH.
True.
The higher the concentration of hydroxide ions in solution, the higher the pH.
If the pH increases by 1, how much does the concentration of hydrogen ions increase by?
If the pH increases by 1, the concentration of hydrogen ions increases by a factor of 10.
Which acids of equal concentrations will have more hydrogen ions in solution, a weak acid or a strong acid?
A strong acid will have more hydrogen ions in solution than a weak acid of equal concentration.
True or False?
The lower the pH, the more acidic the solution.
True.
The lower the pH, the more acidic the solution is.
How many times greater is the concentration of hydrogen ions in a solution of pH 4 and pH 6.
The concentration of hydrogen ions in a solution of pH 4 is 100 times (10 x 10) greater than a solution with a pH of 6.
What is the pH of distilled water?
The pH of distilled water is 7.
If a hydrogen ion concentration in a solution of pH 5 increases by a factor 1000, what is the new pH?
The new pH is 2.
If the hydrogen ion concentration increases by a factor of 10 by the pH decreases by 1. So increase by a factor of 1000 will decrease the pH from 5 to 2.
Define the term strong acid.
A strong acid is an acid that completely dissociates in water, producing a high concentration of H+ ions.
Give an example of a strong acid.
Hydrochloric acid (HCl), sulfuric acid (H2SO4) and nitric acid (HNO3) are examples of strong acids.
True or False?
Weak acids have a pH between 4-6.
True.
Weak acids have a pH between 4-6.
Define the meaning of solute.
A solute is a substance that is dissolved in a solvent to form a solution.
Define the term solvent.
A solvent is a substance, typically a liquid, that dissolves a solute to form a solution.
True or False?
A dilute strong acid can have a lower pH than a concentrated weak acid.
True.
A dilute strong acid can have a lower pH than a concentrated weak acid due to complete dissociation.
What does the ⇌ symbol indicate in the following dissociation of an acid?
CH3CH2COOH ⇌ H+ + CH3CH2COO–
The ⇌ symbol indicates that the acid is weak, an equilibrium is established and the acid only partially dissociates.
What is a concentrated solution?
A concentrated solution contains a large amount of solute in a given volume of solution.
What is a dilute solution?
A dilute solution contains a small amount of solute in a given volume of solution.
What is the difference between a strong and weak acid?
A strong acid dissociates completely in water, while a weak acid only partially dissociates.
What is the difference between a base and an alkali?
A base that is water-soluble is referred to as an alkali. All alkalis are bases, but not all bases are alkalis.
What is the pH range for alkalis?
Alkalis have pH values above 7.
What are the common forms of bases?
Bases are usually oxides, hydroxides, or carbonates of metals.
What happens when ammonia reacts with water?
When ammonia reacts with water, it produces hydroxide ions.
How do basic (alkaline) conditions affect red litmus paper?
In basic (alkaline) conditions, red litmus paper turns blue.
True or False?
Aqueous ammonia and ammonium hydroxide are the same.
True.
Aqueous ammonia and ammonium hydroxide are the same thing.
Which ion is produced in alkaline solutions?
The hydroxide, OH-, ion is produced in alkaline solutions.
Give the general equation for the reaction between a base and acid.
The general equation for the reaction between a base and acid is:
acid + base ⟶ salt + water
Name the type of reaction that occurs when a base reacts with an acid.
The type of reaction is neutralisation.
What is the general equation for the reaction of a metal with an acid?
The general equation for the reaction between a metal and acid is:
metal + acid ⟶ salt + hydrogen
True or False?
All metals react with dilute acids.
False.
Only metals above hydrogen in the reactivity series will react with dilute acids.
State the general equation for the reaction of an acid with a base.
The general equation for the reaction between an acid and a base is:
acid + base ⟶ salt + water
Define the term neutralisation.
A neutralisation reaction is a reaction between an acid and a base to form a salt and water.
True or False?
Effervescence is produced when an acid reacts with a metal oxide or hydroxide.
False.
Effervescence is produced when an acid reacts with a metal carbonate, due to the formation of carbon dioxide gas.
Name the products formed from the reaction between sodium hydroxide and hydrochloric acid.
The products formed from the reaction between sodium hydroxide and hydrochloric acid are sodium chloride and water.
What is the general equation for the reaction of a metal carbonate with an acid?
The general equation for the reaction of a metal carbonate with an acid is:
metal carbonate + acid ⟶ salt + carbon dioxide + water
Write the word equation for the reaction between sodium carbonate and sulfuric acid.
The word equation for the reaction between sodium carbonate and sulfuric acid is:
sodium carbonate + sulfuric acid ⟶ sodium sulfate + water + carbon dioxide
What determines the identity of the salt produced in an acid-base neutralisation reaction?
The identity of the salt produced depends on the acid used and the positive ions in the base.
What substances act as bases in acid-base reactions?
Metal oxides, metal hydroxides and metal carbonates act as bases in acid-base reactions.
Give the test and result for hydrogen gas.
The test and result for hydrogen gas is that a burning splint gives a squeaky pop sound.
Give the test and result for carbon dioxide gas.
The test and result for carbon dioxide gas is that a limewater turns cloudy.
What is the chemical name for limewater?
The chemical name for limewater is calcium hydroxide.
Give the formula of carbon dioxide.
The formula of carbon dioxide is CO2.
Why is it hard to identify hydrogen and carbon dioxide gas?
It is hard to identify these gases as they are colourless and odourless.
Name the method used to prepare a soluble salt from an acid and alkali.
The method used to prepare a soluble salt from an acid and alkali is titration.
Name the piece of equipment which could be used to measure a fixed volume of acid, when preparing a soluble salt.
The piece of equipment which could be used to measure a fixed volume of acid is a pipette.
Give the colour of phenolphthalein in acids and alkalis.
Phenolphthalein is colourless in acids and pink in alkalis.
How are crystals produced from a salt solution?
The solution is heated gently (until crystals start to form) and then left to cool.
How is a soluble salt made?
A soluble salt can be made by the reaction of an acid with an alkali
What is the purpose of adding an indicator?
The purpose of adding the indicator is to visually determine when the acid has neutralised the alkali by observing the colour change.
True or False?
The same volume of acid is added again to the alkali without indicator.
True.
The same volume of acid determined from the titration is added again to the same volume of alkali, but without the indicator this time.
State what is meant by an ionic compound.
An ionic compound consists of a giant lattice of positively charged metal ions and negatively charged non-metal ions.
Define the term insoluble.
Insoluble means the substance is unable to dissolve in a solvent, usually water.
True or False?
All ionic compounds are soluble in water.
False.
Not all ionic compounds are soluble in water, some are insoluble.
True or False?
Sodium carbonate is soluble.
True.
Sodium carbonate is soluble.
True or False?
Compounds of potassium are soluble.
True.
Compounds of potassium are soluble.
True or False?
Compounds of sodium are insoluble.
False.
Compounds of sodium are soluble.
Give three examples of insoluble sulfates.
Three examples of insoluble sulfates are:
barium sulfate
calcium sulfate
lead(II) sulfate
True or False?
All nitrates are insoluble.
False.
All nitrates are soluble.
Give an example of a soluble hydroxide.
Examples of soluble hydroxides include:
sodium hydroxide
potassium hydroxide
calcium hydroxide
True or False?
Silver chloride is soluble.
False.
Silver chloride is insoluble.
What is an insoluble salt?
An insoluble salt is a salt that does not dissolve in water or other solvents.
True or False?
Insoluble salts can be prepared using a precipitation reaction.
True.
Insoluble salts can be prepared using a precipitation reaction.
Define precipitation reaction.
A precipitation reaction is a reaction where an insoluble solid (precipitate) is formed from two soluble reactants
What is meant by a precipitate?
A precipitate is an insoluble solid that is formed from a reaction between two soluble reactants.
What does the method for preparing an insoluble salt involve?
The method for preparing an insoluble salt involves measuring out a fixed volume of one solution and then adding the second salt solution until it is in a slight excess, to ensure the maximum amount of precipitate will be obtained.
True or False?
The precipitate is recovered by evaporation.
False.
The precipitate is recovered by filtration and then it must be washed with distilled water to remove reactants that are contaminating the residue (recovered solid).
Give an example of an insoluble salt often made by precipitation.
Examples of salts made by precipitation include silver and lead(II) salts e.g. lead(II) iodide, silver chloride.
Why is the precipitate washed with distilled water?
The precipitate is washed with distilled water to remove traces of the solutions it was made from.