Chemical changes Flashcards
What is the pH scale?
It is a measure of how acidic or alkaline a solution is.
If a substance is greater than 7 what does this mean?
It is more alkaline.
If a substance is less than 7 what does this mean?
It is more acidic
The further away the substance is from 7 what does it mean?
the stronger the acid or alkaline.
What is the pH of a neutral substance?
pH7
Give an example of a Neutral substance.
Pure water
From pH 1 to 6 what is the colour on uniserval indicator?
Dark red to orange.
What colour on universal indicator is a neutral substance?
Green
From pH 8to 14 what is the colour on uniserval indicator?
green to dark blue
What are the two ways to measure pH of a solution?
1) pH probe
2) indicator of universal indicator.
What is a Universal indicator?
It gives you pH measurement based on color on chart
What is a pH probe?
A digital device which is put in a beaker and give you a reading in number
What is an Acid?
it is a substance that dissolved in water to produce H+ ions it has a pH of less than 7.
What is a base?
it is a substance with a pH greater than 7.
What is an Alkaline?
It is a base that dissolves in water to produce hydroxide ions (OH-) it has a pH of greater than 7.
What are the reactions between acids and bases called?
Neutralization
What is the reaction for Neutralization?
Acid + base —– salt + water
In terms of H+ ions and OH- ions what is the neutralization reaction?
H+(aq) + OH- (aq) —- H20(l)
Sodium hydroxide and hydrochloric acid react to produce sodium chloride and
water. Name the type of reaction described
Neutralization
Explain, in terms of ions and molecules, what happens when any acid reacts with
any alkali.
Hydrogen ions/H+ in the acid React with hydroxide ions OH- in the alkali to produce water.
Ammonium chloride is a useful substance made by a similar reaction to the above. Name the acid that would be used to form ammonium chloride.
hydrochloric acid
Hydrochloric acid produces what?
chlorides
What does nitric acid produces?
nitrates
What does sulfuric acid produce?
sulfates
Sodium hydroxide breaks down into what?
Sodium ions and hydroxide ions when dissolved in water.
In aqueous solution what do acid molecules do?
They ionize (split ) and release H+ ions
What is a strong acid?
They fully ionize in aqueous solutions (every acid molecule splits to release H+ ions)
How do you know the reaction with hydrogen and chloride produces a strong acid HCI (aq) —- H+(aq) +Cl-(aq)
The arrow goes in one direction, telling us that the acid has fully ionised.
Name 3 examples of Strong acids.
Sulfuric acid
Nitriic acid
Hydrochloric acid
What is a weak acid?
The acid partially ionises in aqueous solutions ( only a small proportion of acid particles release H+ ions.
How do you a weak acid is being formed in a word equation?
It has a reversible reaction arrow telling us it is a weak acid.
Name 3 examples of Weak acid.
Carbonic acid
Ethanoic acid
Citric acid
What is concentration?
it is a measurement of how much a soluble substance is dissolved in a solvent.
What is concentration measured in?
grams per dm 3 or moles per dm 3
What is the relationship of the pH scale and concentration of hydrogen ions?
the pH scale gives us an idea of the concentration of hydrogen ions (H+)
A strong acid has a pH of what?
1 2 and 3
A weak acid has a pH of what?
4 5 and 6
Why is a weak acid closer to neutral?
it is closer to neutral as they don’t release as many H+ ions as strong acids do.
The more H+ ions in a solution means what?
The lower the pH
What is the concentration in mol/dm3 of H+ ions in a pH of 1?
0.1
What is the concentration in mol/dm3 of H+ ions in a pH of 2?
0.01
What is the concentration in mol/dm3 of H+ ions in a pH of 3?
0.001
What is the concentration in mol/dm3 of H+ ions in a pH of 4?
0.0001
What is the concentration in mol/dm3 of H+ ions in a pH of 5?
0.00001