Acids/Alkalis/Titrations/mole calculations and formulae Flashcards
State a substance with a pH of 4-6
Ethanoic acid (vinegar)
State a substance with a pH of 8-10
Ammonia
State a substance of a pH between 11-14
Sodium hydroxide
State a substance with a pH of 7
Sodium chloride
State the definition of an acid
An acid is a substance that acts as a source of excess hydrogen ions (H+) in a solution
State the definition of an alkali
An alkali is a substance that acts as a source of excess hydroxide (OH-) ions in a solution
State the definition of a base
A substance that neutralizes acids by absorbing hydrogen ions
Is the reaction of CuO(s) + HCl(aq) —-) CuCl2(aq) a reaction of a base and an acid or an alkali and an acid
Base and an acid
(Does not contain OH ions and CuO is insoluble so not aqeous)
Give three examples of three types of substances that can be a base
1)metal carbonate
2)metal hydroxide
3) metal oxide
Write the equation for when sodium hydroxide ionizes (dissociates) with state symbols
NaOH(aq) —) Na+(aq) + OH-(aq)
Write the equation for when sulfuric acid ionizes
H2SO4(aq) —-) 2H+(aq) + SO4 2-(aq)
What colour does litmus turn in acid and then alkali solutions
Acid= red
Alkali= blue
What colour does methyl organge turn in acid and then alkali solutions
Acid= Red
Alkali= Yellow
What colour does phenolphthalein turn in acid and then alkali solutions
Acid= colourless
alkali= pink
Name four method that can be used to measure pH
Litmus
Universal indicator
Methyl orange
Phenolphthalein
What colour is methyl orange in neutral solutions
Yellow
If the number of H+ ions in a solution decreases, does the pH increase or decrease
Increases
What colour is litmus in neutral solutions
Purple
What colour is phenolphthalein in neutral solutions
Colourless
What is a neutralization reaction
A reaction between an acid and a base
Write the ionic equation of the reaction between Sodium hydroxide and hydrochloric acid
(All neutralization reactions have same ionic equation btw)
OH-(aq) + H+(aq) —-) H2O
(Sodium and chloride ions are same on both side so not included in equation)
Write the equation for the reaction of copper (ii) oxide and dilute sulfuric acid
CuO + H2SO4 —-) CuSO4 + H2O
(Copper oxide + sulfuric acid —-) copper sulphate + water)
Definition of a strong acid
Acid in which ions have completely dissociated
Definition of a weak acid
Acid in which ions have only partially dissociated
What is a titre
The volume of acid or alkali being added
So the difference between the initial reading on the biuret and the final reading
Explain how to carry out a neutralization titration using phenolphthalein, where trying to calculate how much sodium hydroxide is needed to neutralize hydrochloric acid
1)Use a pipette and pipette filler (for safety) to measure 25cm3 of hydrochloric acid and add to a conical flask
2)Add a few drops of phenolphthalein indicator to the conical flask
3)Fill the burette with sodium hydroxide and take initial reading to 2 decimal places
4) keep adding drops to flask and swirling it until solution turns pink
5measure final reading and repeat experiment until concordant results are obtained
Explain Why it is better to use phenolphthalein rather than universal indicator in a titration (2)
Phenolphthalein has only two colours
But universal indicator has a range of colours
The colour change in phenolphthalein us sudden
But the colourless change in universal indicator is gradual
so the exact amount at which the neutralization occurs would be unknown in universal indicator
When recording measurements on a burette how many decimal places should it be till?
2 decimal places
(Burette is the long dagger tube thing)
Explain how you can carry out an experiment using reduction to test the empirical formula of copper oxide
1)measure the mass of a test tube that has a bung with a hole in it
2) place copper oxide inside and measure the mass again
3)turn hydrogen gas on and insert it through the hole in the bung and then begin to pass heat over the test tube
4)once black copper oxide has turned a brown-pink colour weigh the mass of the test tube again as a final reading
5)the initial mass of copper oxide will be (mass of test tube + copper oxide - mass of test tube)
6)the final mass of copper oxide will be (mass of test tube+ final mass of copper oxide - mass of test tube)
7)mass of final copper oxide - initial mass of copper oxide = mass of oxygen
Why can you not find the molecular formula of NaCl
Because it is an ionic compound and is not made up of molecules
H20 + HCL —-) H3O+ + CL-
So explain why the chlorine atom has a negative charge on the products side
Because the H+ ion left an electron behind when it transferred to the water molecule
Definition of an acid, in terms of proton transfer
defined as a proton (or hydrogen ion) donor
Definition of a base (in terms of proton transfer)
Defined as a proton (hydrogen ion) acceptor
Write the ionic equation of the reaction between water and hydrochloric acid (in terms of proton transfer)
H2O(l) + HCL(aq) —-) H3O+(aq) + CL-(aq)
Write the ionic equation of the reaction between ammonia and hydrochloric acid (in terms of proton transfer)
NH3(aq) + HCL(aq) —-) NH4+(aq) + CL-(aq)
