Chem Quiz 5 Flashcards
pH lower than 7
acid
pH greater than 7
base
Turns litmus red and phenolphthalien colourless.
acid
Turns litmus blue and phenolphthalien pink.
base
electrolyte
acid and base
what is an electrolyte?
A substance that conducts electricity when dissolved ions in solution.
Reacts with metals to form hydrogen gas and a salt.
acid
Doesn’t react with non-metals.
Base
Reacts together to form water and a salt.
acids and bases
What happens in a neutralization reaction when the base contains carbonate, bicarbonate.
carbon dioxide is also produced.
sour taste
acid
bitter taste
base
WHAT SHOULD YOU NEVER DO IN A CHEM LAB?
TASTE THE SUBSTANCE!!!!!!!!!!
List the properties of acids.
pH lower than 7, turns litmus red, turns phenophthalien colourless, electrolyt, reacts with metals to form Hydrogen and a salt, reacts with bases to form water and a salt, tastes sour.
List the properties of bases.
pH greater than7, turns litmus blue, turns phenophthalien pink, electrolyte, don’t usually react with non-metals, reacts with acids to form water and salt, tastes bitter.
What is colourimetry?
A technique used to determine the concentration of a colourless compound in a solution.
Explain how a spectrophotometer works.
A light source is sent through a lens. It reaches a prism and there is a slit that only allows out one colour. The coloured light passes through the sample in cuvette and the detector tells you the absorbance of whatever colour.
What does a spectrophotometer find?
The absorbance of a certain colour in a coloured substance.
What are the 3 ways to measure pH?
acid-base indicator, universal indicator, pH meter.
What is an acid-base indicator?
A chemical substance which changes colour with a change in pH. (litmus, phenolphthalein).
What are the pros and cons of acid-base indicators?
Pros: inexpensive, easy to use.
Cons: not very precise.
What is a universal indicator?
A combination of acid base indicators. (wide range pH paper).
What are the pros and cons of using universal indicators?
Pros: easy to use, more precise than acid-base indicators.
Cons: more expensive than an acid base indicator.
What are the pros and cons of using a pH meter?
Pros: most precise method of measuring pH.
cons: expensive, having to calibrate them before use.
Place the 3 ways of measuring pH in order from most precise to least precise.
pH meter, universal indicator, acid-base indicator.
According to the acid-base theories of Arrhenius what is an acid?
A substance that ionizes in water to produce hydrogen ions H+.
Show how HCL ionizes in water.
HCL (aq) ->H+(aq) + Cl-(aq)
According to the acid-base theories of Arrhenius what is a base?
A substance that dissociates in water to produce hydroxide ions OH-.
Show how NaOH dissassociates.
NaOH(aq)-> Na+(aq) + OH-(aq)
List the properties of a strong acid.
Ionizes 100% in water, high conductivity, lower pH.
Why are strong acids highly conductive?
Because they ionize 100%.
Why do strong acids have a lower pH?
Because they have more hydrogen ions.
What are the strong acids that we have to know?
HCl, HI, HBr, HNO3, H2SO4, HClO4.
Show how acetic acid ionizes in water.
CH3COOH(aq) H+(aq) + CH3COO-(aq).
Doesn’t ionize completely.
What are the properties of strong bases?
Dissociate completely when dissolved in water.
Which are the strongest bases?
Hydroxides of group 1 and 2 metals.
What are the strong bases we have to know?
LiOH, NaOH, KOH, RbOH, CsOH, Mg(OH)2, Ca(OH)2, Ba(OH)2, Sr(OH)2.
Show how NH3 reacts with H2O.
NH3(g) + H2O(l) NH4+(aq) + OH-(aq).
What group of metals is always soluble in water?
Alkali metals.
