Chapter 8 - Acid and Alkalis Flashcards
What is neutralisation?
A chemical reaction where an acid and a base produce a solution of neutral pH 7
What is the general word equation for an acid and base ?
Acid + base = salt + water
What pH do acids have? What about alkalines?
Acid pH less than 7, <7
Alkalines pH more than 7, >7
What are bases?
Substances that neutralise acids , they can be soluble bases, alkalines, and other insoluble bases
What are metal oxides?
Insoluble bases, not alkaline
What are hydroxides?
An alkaline base, soluble
What are the main stages of making a soluble salt crystals from dilute sulfuric acid and copper oxide?
Start with a measured volume of acid
Gently heat the acid until almost boiling
Slowly add copper oxide and stir with glass rod, keep adding this until there is excess oxide at the bottom
Remove excess oxide with filter tunnel and paper
Take copper sulfate solution into evaporating basin
Place over Bunsen until half solution is evaporated
Place on widow sill to slowly evaporate and form crystals
What is the general word equation for metal and acid?
Metal + acid = salt + hydrogen
What is the general word equation for metal carbonate and acid?
Metal carbonate + acid = salt + water + carbon dioxide
What is the symbol for carbonate?
CO3
What does diatomic mean?
Chemicals that go around in pairs, e.g. H + Cl
Name the 4 state symbols
Solid (s), gas (g), liquid (l), and aqueous (aq) which means dissolved in water
Alkali does what to the pH? What about acids?
Alkaline increase the pH, acid decreases the Ph
What is the sequence of events to produce a soluble salt from an acid and an alkaline using titration?
Put the acid in the burette (measured amount)
Measure known amount of alkaline in pipette then put this in a conical flask
Add a suitable indicator to the alkali
Slowly add acid from burette whilst stirring
Once alkaline is neutralised (you can see from indicator) measure how much acid that took (from what’s left over)
Repeat this with known amounts and no indicator then evaporate until half way then leave to form salt crystals
What is the name of the method used to to make a salt from an acid and an alkaline?
Titration
What is the acid ion? What about alkaline?
Acid, H+
Alkaline, OH-
What are precipitates?
Solids suspended in a solution, they make the solution cloudy
Solution + solution makes what?
A soluble salt and a non-soluble salt (precipitate)
What does silver nitrate + sodium chloride equal?
Sliver chloride + sodium nitrate
What is the symbol for nitrate?
NO3-
Name the 4 main hazard symbols
Toxic, danger to environment, corrosive and flammable
What dissociates in an acidic solution? What about in an alkaline solution?
H+ ions dissociate in an acidic solution, OH- ions dissociate in an alkaline solution
Name 3 alkaline chemicals and give their formulas
Sodium Hydroxide, NaOH
Calcium Hydroxide, Ca(OH)2
Potassium Hydroxide, KOH
Name 3 acids and give their formula
Hydrochloric acid, HCl
Sulfuric acid, H2 SO4
Nitric acid, HNO3
Name some safety precautions you should take when handling acids and alkalines
Where goggles, gloves if it is corrosive and cover skin
To get to a pH of 1 from 3 what do you have to times the relative concentration by?
100 , 10 x 10
What is a strong acid?
An acid where the H+ ions are fully ionised/ dissociated, such as in HCl where all the Hs are H+ and all the Cls are Cl-. The solution can also be concentrated so that there is a lot of solute relative to the space it’s in, but it can be a dilute strong acid as well
What colour does litmus paper go in acids and alkalines?
Red litmus paper goes blue in alkalines
Blue litmus paper goes red in acids
What colour do alkalines go in phenolphthalein indicator? What about acids?
Alkalines go a pink colour
Acids go colourless
What is a weak acid?
An acid that will partially dissociated in solution e.g. CH3 COOH = CH3 COO- + H+. They can also be dilute so have a relatively small amount of acid in an area, but you can also have concentrated weak acids
Why does acid + metal carbonate = salt + water + carbon dioxide?
Carbonate = CO3
This make carbon dioxide, CO2 and one extra oxygen joins with dissociated H2+ from acid to from H2 O
What is thermal decomposition?
The heating of a metal carbonate to form:
Thermal decomposition = metal oxide + carbon dioxide
What is the difference between indicators like litmus paper and universal indicator?
Most indicators like litmus only show whether the substance is alkaline or acidic unlike universal which shows how strong it is as well and changes colour gradually
What else can you use to give a ph reading which is quite accurate? What might you need to do before using it to make sure it’s accurate?
A ph meter, you might need to calibrate it first
Give some examples of solid acids
Citric acids, tartaric acids
Give some examples of liquid acids
Nitric acid, ethanoic acid, sulfuric acid
What salts are soluble? Include majorities and exceptions
Those that contain sodium, potassium or ammonium (including carbonates and hydroxides)
All that contain nitrates
Most that contain chloride (except sliver and lead)
All those containing sulfates (except lead, barium and calcium)
What salts are insoluble? Include majorities and exceptions
Most that contain carbonates and hydroxides (except those of sodium, potassium and ammonium)
And silver and lead bromides, iodides and bromides
And lead, barium and silver Sulfates
Where is the important insoluble salt, barium sulfate, used?
In medical imaging to diagnose intestinal problems, barium sulphate is opaque to X-rays, shows up on image
What would the heating of solid calcium carbonate form?
Calcium oxide and carbon dioxide
What happens when you heat a carbonate with a hot flame?
It produces (metal oxide and carbon dioxide) a brilliant white light that is used as the limelight in theatres
What are the 2 ways metal carbonates react?
They heat/ thermal composition to form a metal oxide and carbon dioxide
OR they react with an acid to form a metal salt, water and carbon dioxide
What does a bluish green copper carbonate give off/ leave when it is burned?
A colourless gas of carbon dioxide and leaves behind black solid copper oxide, this is thermal decomposition
How can carbon dioxide be tested?
With lime water, carbon dioxide makes lime water milky
