Chapter 4 Acids and Redox

A substance which released hydrogen ions H+, protons, when dissolved

An acid with fully disassociates when dissolved, releases all of its hydrogens ions into solution

A substance which partially disassociates when dissolved, releasing some of its hydrogen ions into solution

A substance which neutralises an acid to form a salt, accepts protons

A substance which releases hydroxide ions OH- when dissolved, a soluble base

When an acid and base react to form a salt and neutral water

The product of when a H+ ion is replaced a metal ion or ammonium ion

Sodium Propanoate

Calculating Concentrations Identification of unknown substances Verifying purity

Weigh the solid in a weighing boat very accurately Transfer the solid to a small beaker and add a minimal amount of water, only sufficient enough to allow the solid to dissolve fully. Use a glass rod to stir. Transfer the solution to a volumetric flask using a funnel. Rinse the weighing boat, beaker, glass rod, and finally funnel to the volumetric flask, to ensure all of the solid has been accounted for, no traces remain. Fill the volumetric flask with distilled water. When close to the graduation line, add drop wise. The bottom of the meniscus should align with the graduation line Place the stopper. Invert several times to mix.

(Uncertainty burette/titre) x 2 x100

Using a pipette and pipette filler to measure and transfer 25cm3 of NaOH to a conical flask Add a few drops of a single indicator such as phenolphthalein (purple in base, colourless acidic). Set up a burette. Add an excess amount of HCl to the burette. Place the conical flask on a white tile underneath the tap of the burette. Record the value of acid in the burette. Open the tap and close when the colour in the flask changes. Record this final value in the burette. The titre is the final volume - initial volume. This first tire is the rough titre. Repeat the experiment, swirling the conical flask as you go. When the colour changes but reverts, add the acid drop wise. Repeat until concordant results

Titre is the volume of solution used to neutralise the other solution Concordant titres are those which are within 0.10cm3 of each other

Only concordant values

For concertation: n=Cv, ratio, C=n/v For substance: n=Cv, ratio, scale up to number of moles in standard solution, Mr=mass/n

A system used to show the number of electrons involved in bonding to a different element

Ensuring all electrons have been accounted for Formulae and Balancing Oxidation and Reduction of covalent compounds

Elements alone (or bonded to each other) have an oxidation number of Place the sign in front of the number Each atom in a compound has an individual oxidation number The sum of the oxidation numbers is equal to the charge of the compound Use the ion charge most of the time O is normally -2, H is usually +1

O is peroxides (oxygen bonded together to other elements) = -1 H in metal hydrides = -1 O bonded to F= +1

For elements with multiple oxidation states (transition metals, Cl, N…) use Roman numerals to show oxidation state, for when not obvious E,g Iron(II) dichromate vs Iron(III) dichromate FeCr2O7 vs Fe2(Cr2O7)3

Oxidation is the gain of oxygen. Reduction is the loss of oxygen.

Oxidation is the loss of electrons. Reduction is the gain of electrons.

Oxidation is the increase is oxidation number. Reduction is the decrease in oxidation number

Redox reactions are where oxidation and reduction occur in the same reaction Disproportion is when the same elements is both oxidised and reduced in the same reaction