Y10 Science Acids and Bases Flashcards
(24 cards)
Define acid
A substance that donates H+ ions to water.
Define base
A substance that accepts H+ ions from water (forming OH- ions).
What are the properties of an acid?
Taste sour.
Has more hydrogen ions.
pH 0 to 6.
UI turns red, orange and yellow.
Blue litmus paper turns red.
It is corrosive
Common examples:
HCl, HNO3, H2SO4, CH3COOH
What are the properties of a base?
Taste bitter.
Has more hydroxide ions.
pH 8 to 14
UI turns dark green, blue and purple.
Red litmus paper turns blue.
It is caustic
Common examples:
NaOH, CaCO3, NH3, NaHCO3
Name common lab acids
Acids - Contain hydrogen ions (H+)
HCl - Hydrochloric acid
HNO3 - Nitric acid
H2SO4 - Sulfuric acid
CH3COOH - Ethanoic acid
.
Name common lab bases
Bases - Produce hydroxide ions (OH-)
NaOH - Sodium hydroxide
CaCO3 - Calcium carbonate
NH3 - Ammonia
NaHCO3 - Sodium hydrogen carbonate
.
What is concentration?
The measure of the amount of solute dissolved in a given volume of solvent measured in gL-1.
Describe concentration using the examples of acids and bases
An acid when it has water added to it, will become more dilute. There will be less H+ ions in a given volume, eg. if the volume is 50ml and the number of H+ ions is 20, if more water is added and the total volume is now 250ml. Then the 20 H+ ions are now spread out over a larger volume. They are more dilute and therefore the pH will increase as it becomes less acidic.
Similarly, for a base which contains OH- ions. If there are 20 OH- ions in 50ml, and it is diluted by adding water to 250mls then the 20 OH- ions are now spread out over a larger volume. This solution is now more dilute and the pH is lower as it is less basic.
What is the formula to concentrate a solution?
c=m/V
What units are mass (m) and volume (V) in in the concentration formula?
Mass: Grams
Volume: Litres
How do you classify acids and bases using litmus paper?
If both the blue and red litmus paper remain the same when put in the substance then it is neutral.
If blue litmus turns red and red litmus remains the same it is an acid.
If blue litmus stays blue and red litmus turns blue it is a base.
How do you classify acids and bases using universal indicator?
If it’s red/orange/yellow it’s an acid.
If it’s green it’s neutral.
If it’s blue/purple it’s a base.
What does pH stand for?
Power of Hydrogen.
What is the pH scale? And what differentiates it from acid and base? Talk about the concentration of both hydrogen ions and hydroxide ions.
pH 1 → 6 = Acids (a solution with a pH of 1 has a very high concentration of hydrogen ions whereas a solution with a pH of 6 has a high concentration of hydrogen ions)
pH 7 = Neutral (an equal concentration of hydrogen ions and hydroxide ions)
pH 8 → 14 = Base (a solution with a pH of 8 has a low concentration of hydrogen ions and a solution with a pH of 14 has a very low concentration of hydrogen ions)
Always talk about BOTH ions (H+ and OH-]
What is the concentration of ions in relation to the pH of the substance?
1 - 2 very acidic [H+] is much greater than [OH-]
3 -6 slightly acid [H+] is greater than [OH-] but less than for pH 1-2
7 neutral [H+] = [OH-]
8 - 11 slightly basic [OH-] is greater than [H+] but less than [OH-] for pH 12-14
12 - 14 very basic [OH-] is much greater than [H+]
What is the advantage of UI over litmus paper?
Universal Indicator (UI) gives you an idea of the pH value because each colour indicates a relative concentration of OH- and H+. The colour of the UI indicates how acidic or basic a solution is. Litmus paper only shows if a substance is an acid, base, or neutral and doesn’t tell us the degree of acidity or basicity (very acidic, slightly acidic, very basic, or slightly basic). Universal indicator gives an approximate value of the pH of the substance.
Define neutralisation reactions
A neutralisation reaction is when an acid reacts with a base forming a salt. Additionally, in the process H+ ions combine with OH- ions to form water, H2O.
This results in a solution with a pH of 7, which has an equal [H+] to [OH-].
.
Describe how acids react with metals
When an acid reacts with a metal, a metal salt and hydrogen gas are formed as the products.
This can be observed through the solid metal disappearing, bubbles appearing in the reaction vessel and the reaction vessel will change temperature.
.
Describe how acids react with metal carbonates
When an acid is added to a metal carbonate, a metal salt, water, and carbon dioxide gas are formed as the products.
This can be observed through the solid metal carbonate disappearing, bubbles appearing in the reaction vessel and the reaction vessel will change temperature.
How do you test for Hydrogen gas?
Pop Test - Test for Hydrogen Gas
To test that the reaction produces hydrogen gas, you need to collect the gas from the reaction and put a burning splint near the gas. If there is a squeaky pop sound, hydrogen is present. This is called the pop test.
.
How do you test for Carbon dioxide?
Limewater Test - Test for Carbon Dioxide
To test that the reaction produces carbon dioxide gas, you can collect the gas (using a bung and delivery tube) and bubble it through limewater, the limewater will go from colourless to milky/cloudy (as a white solid is produced). This is evidence of carbon dioxide gas.
What is a neutralization reaction?
Acid + Base → Metal salt + Water
What is metal acid reaction?
Metal + Acid → Metal salt + Hydrogen gas
What is a metal carbonate acid reaction?
Acid + Metal carbonate/hydrogen carbonate → Water + Metal salt + Carbon dioxide
