Ch - 11 (Acids and Bases) Flashcards
What happens when acids are added to water?
Form positively charged hydrogen ions. (H+)
What makes a solution acidic?
Presence of H+ ions.
Give a word equation of acids reacting with metals?
Acid + Metal –> Salt + Hydrogen
Which metals in the reactivity series will react with dilute acids?
Metals above hydrogen
What can act as bases?
- Metal oxides
- Hydroxides (alkalis)
Give a word equation of acid reacting with base.
Acid + base –> Salt + water
Give an equation of the acid reacting with a metal carbonate.
Acid+ metal –> salt + carbon dioxide + water
What is one common indicator?
Litmus extracted from lichens
What are synthetic indicators?
Organic compounds that are sensitive to changes in acidity and appear different colours in acids and alkalis.
What are 2 synthetic indicators frequently used in acid - alkali titrations?
Thymolphthalein and methyl orange
What are synthetic indicators used for?
To show the endpoint in titrations as they have a very sharp change of colour when an acid has been neutralised by an alkali or vice versa.
Is litmus suitable for tritration? why or why not?
colour change is not so sharp, colour in neutral solution makes it difficult
What pH does a base have?
Above 7
What is a base?
water soluble referred to as an alkali
In basic (alkaline) what colour do the following change into:
- red litmus paper
- methyl orange
-thymolphthalein
- red litmus paper: blue
- methyl orange: yellow
-thymolphthalein: blue
What form are bases of metals?
Oxides or hydroxides
What happens when alkalis are added to water?
Form negative (OH-) ions
What makes a solution an alkali?
Presence of OH- ions
Give a word equation of what happens when acid reacts with bases?
Acid + base –> salt + water
What happens when acids are added to water?
Form positively charged H+ ions (acidic)
What happens when alkalis are added to water?
Forms negative OH- ions (alkali)
When does a neutralisation reaction take place?
When acid reacts with an alkali
What happens when substances react together in a neutralisation reaction?
H+ ions reacts with OH- ions to produce water
What is the net ionic equation of acid - alkali neautralisation reaction?
H+ + OH- –> H2O
What is the pH of all acids?
Below 7
What is the pH of all alkalis?
Above 7
What does it mean when we have more hydrogen ions?
Stronger the acid but lower the pH
What does it mean when we have a stronger concentration of hydroxide ions?
Higher pH
How is the Ph scale calibrated?
Logarithmic, change of 1 on the scale represents a change in concentration by a factor of 10
Define a universal indicator.
A universal indicator is a mixture of different indicators which is used to measure pH.
Define acids
- Proton donors
- Produce H+ protons
Define bases.
- Proton acceptor
How can an acid be weak or strong?
depending on how many H+ ions they produce
What happens to strong acids?
Completely dissociate (ionise) in water, producing very low pH
What are examples of strong acids?
Hydrochloric acid, Sulfuric acids, nitric acid
What is an example of a weak acid?
Ethanoic acid (CH3COOH) - Vinegar
What happens to weak acids in water?
Partially dissociate (ionise) in water and produce pH value closer to the middle lf pH scale below 7
What does a concentrated solution mean?
An acid that contains a higher no. of acid molecules
Define oxides.
Compounds made from one or more atoms of oxygen combined with another element.
How can oxides be classified?
Based on their acid - base characteristic.
What are the difference in properties of acidic and basic oxides?
- Difference in their pH depends on the bonding with a metal or non - metal
- Metallic character of the element influences the acidic or basic behaviour
What are properties of acidic oxides?
- Non - metal combines with oxygen
- React with bases to form salt and water
- When dissolved in H2O, they produce an acidic solution with low pH
Example - CO2, SO2, NO2
What are the properties of basic oxides?
- Metal element combines with oxygen
- React with acids to form salt and water
- When dissolved in H2O, they produce a basic solution with a High pH.
Example: CuO, CaO
what are neutral oxides?
- Do not react with acids or bases
- Example: N2O, NO and CO
Define amphoteric oxides.
- Curious group of oxides tht behave both acidic and basic, depending on reactant being an acid or base
What are properties of an amphoteric oxide?
- Salt and water is formed
- common example: ZnO, Al2O3
- Hydroxides are also amphoteric
