Chapter 4 Flashcards
What is a strong acid?
Releases all its hydrogen atoms into solution as H+ ions and completely dissociates in an aqueous solution
What is a weak acid? What type are weak acids?
Only releases a small proportion of its available hydrogen atoms into solution as H+ ions
Partially disassociates in aqueous solution
Most organic compounds
What are classifies as bases?
Metal oxides, metal hydroxides, metal carbonates and ammonia
Alkalis
What does a base do?
Neutralises an acid to form a salt
What happens in a neutralisation of an acid?
H+ ions react with a base to form a salt and neutral water
H+ ions from the acid are replaced by a metal or ammonium ions from the base
What are the products of CuO (copper oxide)+ H2SO4 (sulfuric acid)?
CuSO4 (copper sulfate) + H2O (water)
What are the products of ZnCO3 (zinc carbonate) + H2SO4 (sulfuric acid)?
-> ZnSO4 (zinc sulfate) + H2O + CO2
Why does sulfuric acid act as a strong acid but HSO4- ions act as weak acids?
As only one of the hydrogen atoms fully disassociates and is released as a H+ ions
What is a titration?
Technique used to accurately measure the volume of one solution that reacts exactly with another solution
What are titrations used for?
- finding concentration of a solution
- identification of unknown chemicals
- finding the purity of a substance
How do you prepare a standard solution?
1) Accurately weigh the solid
2) Dissolve the solid in a beaker using less distilled water than will be needed to fill the volumetric flask to the mark
3) This solution is transferred to a volumetric flask the last traces of the solution are rinsed into the flask with distilled water
4) The flask is carefully filled to the graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up exactly with the mark
5) Invert the the volumetric slowly to mix the solution thoroughly
What are the typical volumetric flasks you’ll use?
100cm3: +- 0.20cm3
250cm3: +- 0.30cm3
What are the pipettes manufactured to?
20cm3 pipette: +- 0.04cm3
25cm3 pipette: +- 0.06cm3
What does we measure the burette reading to?
Nearest +- 0.05
Reading always has 2.d.p
How do you do an acid-base titration?
1) Add a measured volume of one solution to a conical flask using a pipette
2) Add the other solution to a burette and record the initial burette reading to the nearest 0.05cm3
3) Add a few drops of an indicator to the solution in the conical flask
4) Run the solution in the burette into the solution in the conical flask, swirling the conical flack throughout to mix the 2 solutions
5) At the end point there’ll be a colour change
6) Record the final burette reading. The volume of solution added from the burette is called the titre (final - initial burette reading)
7) A quick, trial titration is carried out first to find the approximate titre
8) The titration is then repeated accurately adding solution drop wise as the end point is reached
9) Carry out until titres are concordant
How do you work out the remaining information of the reacting volumes?
1) work out the amount in moles of the solute in the solution for which you know both the concentration and volume
2) Use the equation to work out the amount in moles of the solute in the other solution
3) Work out the unknown information about the solute in the other solution
What is a salt?
When the H+ in an acid is replaced by a metal ion or an ammonium or a + ion
What is an acid?
A proton donor
What is the anhydrous?
Not containing the water of crystallisation
