acids and bases Flashcards
what are the qualities of acid
Acids have a pH below 7
They are corrosive and sour tasting
In acidic conditions blue litmus paper and methyl orange turns red
Acids are proton donors as they ionize in solution producing protons, H+ ions
These H+ ions make the aqueous solution acidic
what are the qualities of bases
Bases have pH values of above 7
They taste bitter and chalky
Bases turn litmus paper blue and methyl orange yellow
A base which is water-soluble is referred to as an alkali
They are metal hydroxides
Bases are usually oxides or hydroxides of metals, except for ammonia
Bases (alkalis) are proton acceptors as they ionize in solution producing OH– ions which can accept protons
These OH– ions make the aqueous solution alkaline
formula of stoichometry for neutralisation reaction
Ma Va = Mb Vb
M =molarity/concentration
V= volume in cm3
a=acid
b=base
what are the steps in analytical titration
Measure amount of unknown concentration solution and place in beaker
Add indicator
Titrate using known concentration until the endpoint is reached
Calculate the concentration of the solution in the beaker
methods to prepare salts
Titration
Titration of acid and alkali to make salt and water
The salt is a soluble salt so you have to crystallise it
The Alkali is the solution
Evaporation method
Needs excess addition of insoluble base/metal with acid
Need to filter then crystallise it
Precipitation
Mixing two solutions of soluble salt to make an insoluble salt
Need to filter then wash/dry it
solubility rule
All K+, Na+, NH4+ = Soluble
All Ethanoate, CH3COO- & Nitrate, NO3- = Soluble
All Carbonate, CO32- = Insoluble, except K+, Na+, NH4+
All Halides (Cl-,Br-,I-)= Soluble, except Ag+, Pb2+
All SO42- = Soluble, except Pb2+, Ba2+, Ca2+
ways to make soluble salts
- acid+alkali titration
- acid+excess insoluble solid (reactive metal, base or carbonate)
ways to make insoluble salts
This involves mixing solutions of two soluble salts that between them contain the ions that make up the insoluble salt. It is made by two methods
- direct combination
- precipitation
how to make a sulfate
use sulfuric acid
how to make a chloride
use hydrochloric acid
what is a strong acid/base
Strong acids and bases ionize completely in water, producing solutions of very low pH for an acid or very high pH for a base
what is a weak acid/base
Weak acids and bases partially ionize in water and produce pH values which are closer to the middle of the pH scale
what is example of strong acids
Strong acids include HCl and H2SO4 and strong bases include the Group I hydroxides
what is an example of weak acids
Weak acids include organic acids such as ethanoic acid, CH3COOH (aectic acid) and weak bases include aqueous ammonia
equilibrium in weak acids and alkalis
For both weak acids and bases, there is usually an equilibrium set-up between the molecules and their ions once they have been added to water
Example of a weak acid: propanoic acid
CH3CH2COOH ⇌ H+ + CH3CH2COO-
Example for a weak base: aqueous ammonia
NH3 + H2O ⇌ NH4+ + OH-
In both cases the equilibrium lies to the left, indicating a high concentration of intact acid / base molecules, with a low concentration of ions in solution
acid + metal
Acids react with metals to form salt and hydrogen
acid + base
Acids react with bases to form salt and water
acid + carbonate
Acids react with carbonates to form salt, water and carbon dioxide
bases + ammonium salt
Bases react with ammonium salts to form salt, water and ammonia
what are some indicators
Universal indicator is a mixture of indicators. It is useful because it shows a range of colours from pH 1–14. pH meter Direct distinction between acid and base Litmus paper Direct distinction between acid and base Universal Indicator DIfferent shades for each pH
what is pH + formula
Stands for potential of hydrogen
Formula is ㏒10(value of mol)
what are oxides
An oxide is a compound of oxygen and another element
what are the four groups of oxides
acidic oxides
basic oxides
amphoteric oxides
neutral oxides
properties of acidic oxides
Acidic oxides are oxides of non-metals (noble gases don’t form acidic oxides)
Acidic oxides are often gases at room temperature
Acidic oxides react with water to form acidic solutions
E.g. sulfur trioxide + water -> sulfuric acid (so3+h20-> H2SO4)
Acidic oxides react with bases and alkalis to produce salts and water
E.g carbon dioxide + sodium hydroxide -> sodium carbonate + water (CO2+2NaOH -> Na2CO3 + H2O)
properties of basic oxides
Basic oxides are oxides of metals, with exception of ammonia (non-
metal base)
Basic oxides are often solids at room temperature
Most basic oxides are insoluble at room temperature
Basic oxides react with acids to produce salt and water
This is known as a neutralisation reaction
E.g magnesium oxide + hydrochloric acid -> magnesium chloride + water (MgO + 2HCl -> MgCl2 + H2O)
When a metal oxide reacts with an acid, the atoms are rearranged
properties of amphoteric oxides
Amphoteric oxides are oxides of metals
Some examples of metals that form amphoteric oxides are aluminum, germanium and zinc
They can behave as acidic oxides or basic oxides
They react with acids and alkalis to produce salts
E.g aluminium oxide + hydrochloric acid -> aluminium chloride + water
E.g aluminium oxide + sodium hydroxide -> sodium illuminate + water
properties of neutral oxides
Neutral oxides are non-metals that form oxides that show neither basic nor acidic properties
They are insoluble in water
what are the neutral oxides?
- water
- carbon monoxide
- nitric oxide/nitrogen monoxide
