C3 Chemical changes Flashcards
What ions does an acid form in solutions?
H+ ions
What ions does a base have?
OH- ions
What is a base?
any substance + acid –> salt + water
What is an alkali?
- a soluble base
- that dissolves in water
- form OH- ions
What colour changes occur on red litmus paper?
acidic solution - red
neutral solution - red
alkaline solution - blue
What colour changes occur on blue litmus paper?
acidic solution - red
neutral solution - blue
alkaline solution - blue
What colour changes occur on litmus paper?
acidic solution - red
neutral solution - purple
alkaline solution - blue
What colour changes occur in methyl orange?
acidic solution - red
neutral solution - yellow
alkaline solution - yellow
What colour changes occur in phenolphthalein?
acidic solution - colourless
neutral solution - colourless
alkaline solution - pink
What is a neutral pH?
7
What is an acidic pH?
1-6
What is an alkaline pH?
8-11
How does the concentration of H+ ions affect pH?
high conc means lower pH
-more acidic
How does concentration of OH- ions affect pH?
high conc means higher pH
-more alkaline
How does H+ ion concentration in a solution affect pH?
As H+ ion conc increases by a factor of 10 pH decreases by 1
eg pH 5 x10H+ —> pH 4
If the pH decreases what has happened to the H+ ion concentration?
increased by a factor of 10
How is concentration different to acid strength?
concentration
-how much acid that is dissolved in 1 dm^3 of water
acid strength
-how much of the acid dissociates to form H+ ions
What is a strong acid?
strong acids completely ionise in water
-> dissociate to release H+ ions
What is a weak acid?
weak acids partially ionise in water
-> some molecules dissociate
ionisation of a weak acid is reversible