RAG - Red Flashcards
Acid + Metal >
Salt + Hydrogen
Acid + Metal Oxide >
Salt + Water
Acid + Carbonate >
Salt + Water + Carbon Dioxide
Acid + Metal Hydroxide >
Salt + Water
Hydrochloric Acid + Magnesium >
Magnesium Chloride + Hydrogen (salt + hydrogen)
Sulfuric Acid + Copper Oxide >
Copper Sulfate + Water (salt + water)
Hydrochloric Acid + Copper Carbonate >
Copper Chloride + Water + Carbon Dioxide (salt + water + carbon dioxide)
Nitric Acid + Sodium Hydroxide >
Sodium Nitrate + Water (salt + water)
What is the method for a neutralisation reaction?
- Use a measuring cylinder to add dilute hydrochloric acid to a beaker.
- Dip a clean glass rod into the contents of the beaker. Use it to transfer a drop of liquid to a piece of universal indicator paper on a white tile. Wait for 30 seconds then match the colour to a pH colour chart and record the pH.
- Add a level spatula of calcium hydroxide powder to the beaker.
- Stir thoroughly, then estimate and record the pH.
- Repeat this until there are no more changes in pH.
Method for crystallisation:
- Place the sulphuric acid in a conical flask and warm it in a warm water bath.
- Add a spatula of copper oxide powder to the acid and stir with a glass rod.
- Continue adding the copper oxide powder until it is in excess.
- Filter the mixture to remove the excess copper oxide.
- Pour the filtrate into an evaporating basin.
- Heat the copper Sulfate solution to evaporate half the water.
- Leave the solution by a window to allow all the water to evaporate.
Method for an acid-Alkali titration:
- Use the pipette and pipette filler to add a measured volume of alkali to a clean conical flask.
- Add a few drops of indicator and put the conical flask on a white tile.
- Fill the burette with acid and note the starting volume.
- Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
- Stop adding the acid when the
end-point is reached (when the indicator first permanently changes colour). Note the final volume reading. - Repeat steps 1 to 5 until you get
concordant titres. - More accurate results are obtained if acid is added drop by drop near to the end-point.
Purpose of using a pipette in a titration:
- to accurately measure the volume of a reactant before transferring it to a conical flask.
Purpose of using a burette in a titration:
- to add small, measured volumes of one reactant to the other reactant.
Naming salts - hydrochloric acid
Chloride salts
Naming salts - nitric acid
Nitrate salts
Naming salts - sulfuric acid
- Produces Sulfate salts
To make a soluble salt from an acid and an insoluble reactant:
- Add some dilute hydrochloric acid to a beaker.
- Add powdered insoluble reactant to some acid in a beaker, one spatula at a time, stirring to mix. The mixture will effervesce. Continue adding powder until some unreacted powder is left over - it is in excess.
- Filter the mixture in the beaker to remove the excess powder.
- Allow the water in the solution to evaporate (by heating and/or leaving for a few days) to obtain pure dry crystals of the salt.
Dilute:
- contains a relatively small amount of dissolved solute
Concentrated solution:
- contains a relatively large amount of dissolved solute
Strong acids:
- Strong acids completely dissociate into ions in solution.
- For example, hydrochloric acid is a strong acid.
- It completely dissociates to form hydrogen ions and chloride ions.
Weak acids:
- Weak acids only partially dissociate into ions in solution.
- For example, ethanoic acid is a weak acid.
- It only partially dissociates to form hydrogen ions and ethanoate ions.
Electrolytes:
- Ionic compounds that are:
- in the molten state (heated so they become liquids).
Or - dissolved in water.
- Under these conditions, the
ions in electrolytes are free to move within the liquid or solution.
Electrolysis:
- a process in which electrical energy, from a direct current (dc) supply, decomposes electrolytes.
- The free moving ions in electrolytes are attracted to the oppositely charged electrodes, which connect to the dc supply.
Cations:
- Positively charged ions are called
cations. - They move towards the negatively charged electrode, which is called the cathode.
Anions:
- Negatively charged ions are called
anions. - They move towards the positively charged electrode, which is called the anode.
Products of electrolysis - cations
- gain electrons from the negatively charged cathode
Products of electrolysis - anions:
- lose electrons at the positively charged anode
Molten lead bromide, PbBr2(l), is an electrolyte. During electrolysis:
- Pb2+ ions gain electrons at the cathode and become Pb atoms.
- Br- ions lose electrons at the anode and become Br atoms, which pair up to form Br2 molecules.
- So lead forms at the negative electrode and bromine forms at the positive electrode.
Why can pure water conduct?
- because a small proportion of its
molecules dissociate into ions. - The two ions formed in water are, hydrogen ions, H+, and hydroxide ions, OH-.
During the electrolysis of water:
- H+ ions are attracted to the
cathode, gain electrons and form hydrogen gas. - OH- ions are attracted to the anode, lose electrons and form oxygen gas.
Hydrogen production at the cathode:
- the metal is produced at the cathode if it is less
reactive than hydrogen. - hydrogen is produced at the cathode if the metal is more reactive than hydrogen.
Production at the anode:
- Either oxygen or a non-metal from the electrolyte can be produced at the anode:
- for the most common compounds oxygen is produced (from the hydroxide ions)
- if halide ions (chloride, bromide or iodide ions) are present, then the negatively charged halide ions lose electrons to form the corresponding non-metal halogen (chlorine, bromine or iodine).
Investigate electrolysis of copper Sulfate solution using inert electrodes:
- Pour some copper sulfate solution into a beaker.
- Place two graphite rods into the copper sulfate solution. Attach one electrode to the negative terminal of a dc supply, and the other electrode to the positive terminal.
- Completely fill two small test tubes with copper sulfate solution and position a test tube over each electrode as shown in the diagram.
- Turn on the power supply and observe what happens at each electrode.
- Test any gas produced with a glowing splint and a burning splint.
- Record your observations and the results of your tests.
Investigate electrolysis of copper Sulfate solution using copper electrodes:
- Pour some copper sulfate solution into a beaker.
- Measure and record the mass of a piece of copper foil. Attach it to the negative terminal of a dc supply, and dip the copper foil into the copper sulfate solution.
- Repeat step 2 with another piece of copper foil, but this time attach it to the positive terminal.
- Make sure the electrodes do not touch each other, then turn on the power supply. Adjust the power supply to achieve a constant current as directed by your teacher.
- After 20 minutes, turn off the dc supply.
- Carefully remove one of the electrodes. Gently wash it with distilled water, then dip it into propanone. Lift the electrode out and allow all the liquid to evaporate. Do not wipe the electrodes clean. Measure and record the mass of the electrode.
- Repeat step 6 with the other electrode. Make sure you know which is which.
- Repeat the experiment with fresh electrodes and different currents.
What happens during the process of purification of copper by electrolysis:
- Four Cu ions are attached to the rod on the right, and four Cu²+ ions are floating in the space between the rods.
- A battery is connected between the rods and the Cu ions are pulled towards the left rod.
- There are now four Cu ions attached to the left rod, with four Cu²+ ions floating in the middle.
Purifying copper by electrolysis - how does pure copper form on the cathode?
- A beaker with pure and impure copper rods dipped into copper sulfate solution.
- The pure copper rod is connected to the negative terminal of a battery and the impure rod is connected to the positive terminal.
- The pure copper rod has increased in size while the impure rod has deteriorated, leaving a pool of anode sludge at the bottom of the beaker.
Oxidation is:
The loss of electrons.
Where does oxidation happen?
The anode
What is reduction?
- The gain of electrons
Where does reduction happen?
The cathode
the more reactive a metal is:
- the more vigorous its reactions are
- the more easily it loses electrons in reactions to form positive ions
Metal + water >
Metal Hydroxide + Hydrogen
Metal + Acid >
Salt + Hydrogen
A metal’s relative tendency to form cations and its resistance to oxidation are both related to its position in the reactivity series. In general:
- the higher up a metal, the greater the tendency to form cations
- the lower down a metal, the greater its resistance to oxidation