Topic 3 - Chemical Changes Flashcards
Aqueous Solutions
Something that has been dissolved in water
( can either be acid, alkaline or neutral )
PH scale
Mesures how acidic or alkaline something is
0 - 6 = Acid
7 = Neutral
8 - 14 = Alkaline
Indicators
Substances that change color depending on the PH
What are 3 common Universal Indicators?
Litmus, Methyl Orange and Phenolphthalein
What is the color range of Litmus in PH ?
Alkaline = blue
neutral = purple
Acidic = Red
What is the color range of methyl orange in PH?
Alkaline / = Yellow
Acid = Red
What is the color range of phenolphthalein in PH
Alkaline = Pink
Acid / Neutral = Colorless
Ion
An atom that has a net charge through loosing or gaining electrons
( metals always make a + ion)
Polyatomic Ions
Groups of atoms held together by covalent bonds, has a net charge.
What do acids do when in water? How does this cause their Ph?
They dissociate/ ionise - they form H+ ions in water. As the concentration of H+ ions increases, the Ph decreases
What is the formula for hydrochloric acid?
HCl
What is the formula for sulfuric acid?
H2SO4
What is the formula for nitric acid?
HNO3
What is the formula for sodium hydroxide
NaOH
What is the formula for Potassium hydroxide
KOH
What is the formula for Calcium hydroxide?
Ca(OH)2
How does Hydrochloric acid dissociate when in water?
HCL –> H+1 + Cl-4
How does Sulfuric acid dissociate when in water?
H2SO4 —-> H+2 + SO-2
How does nitric adis dissociate when in water?
HNO3 –> H+ + NO3 -
What do acids produce when dissociating in water?
Hydrogen ions
H+
What do alkalis produce when dissociating in water?
Hydroxide ions
OH-
What is Ph a mesure of ?
How many hydrogen ions are in a solution.
More H+ = Higher concentration = lower PH = More acidic
More hydroxide = more alkaline
hydrigen ions are equal to hydroxide ions = neutral PH
What is the Equation for concentration?
Con (g/dm3) = Amount dissolved / Volume of solution
what is the unit for concentration?
Grams per decimetre cubed or g/dm3
What is a dm3
cm3 times 1000
What difference is there between different PH?
x 10 or / 10
PH 6 x 10 = PH 7
Bases
substances that reacts with (neutralises) acids to form a salt and water only
What is the equation or bases and salts?
Metal oxide + acid —-> salt + water
Neutralisation
The chemical reaction in which a base is mixed with and acid to form a water and salt
How does an acid become neutal in neutralisation?
During neutalisation, hydrogen ions in the acid combine with oxide ions to form water. this removes the hydrogen and so the ph increases
How is a solution more acidic?
That solution will have a higher concentration of hydrogen ions
( as the concentration of H+ increases, the PH decreases)
What is a common base?
Metal Oxides ( they are basic/ alkaline)
What does acid strength tell you?
what proportion of the acid molecules ionise in water
more ionise = higher concentration of Hydrogen ions = lower PH
What are some strong acids?
Nitric, sulfuric, hydrochloric