Acids, bases and salt preparations Flashcards
What are the general rules for predicting the solubility of ionic compounds in water?
- Sodium, potassium, and ammonium compounds are soluble.
- All nitrates are soluble.
- Common chlorides are soluble, except those of silver and Lead (II).
- Common sulfates are soluble, except for those of barium, calcium, and Lead (II).
- Common carbonates are insoluble, except for those of sodium, potassium, and ammonium.
- Common hydroxides are insoluble, except for those of sodium, potassium, and calcium (calcium hydroxide is slightly soluble).
Define acids and bases in terms of proton transfer.
- Acids are proton donors.
- Bases (Alkalis) are proton acceptors.
Describe the reactions of hydrochloric acid with metals, bases, and metal carbonates.
- Acid + base → salt + water
- Acid + metal → salt + hydrogen
- Acid + metal carbonate → salt + water + carbon dioxide
How can you prepare a pure, dry sample of a soluble salt from an insoluble reactant?
- React an acid with an insoluble base in excess.
- Remove excess base by filtration to obtain only the salt and water.
What is the formula for sodium hydroxide, and what ions does it form in water?
- Formula: NaOH
- Ions formed in water: Na+ and OH-
Explain the role of an insoluble reactant in the preparation of a soluble salt.
- The insoluble reactant is added in excess to ensure all acid reacts, preventing dangerous concentration during evaporation.
- Excess reactant is then removed by filtration, leaving only the salt and water.
How can you prepare an insoluble salt from two soluble reactants?
- Precipitate reaction
- Add soluble salts to water and mix
- Filter to remove precipitate from the mixture
- wash it with distilled water to remove traces of solution, and let it dry in an oven.
Provide the method to prepare a sample of pure, dry-hydrated copper(II) sulfate crystals from copper(II) oxide
- place some sulfuric acid in a conical flask and warm it in a water bath
- add a spatula of copper oxide powder to the acid and stir with a glass rod
- continue adding copper oxide powder until it is in
excess - filter the mixture to remove the excess copper oxide
- pour the filtrate (the copper sulfate solution) into an evaporating basin
- heat the copper sulfate solution to evaporate half of the water
- pour the solution into a watch glass and leave to allow all of the water to evaporate
An insoluble salt is prepared by mixing solutions of silver nitrate and sodium chloride.
State the name of the insoluble salt formed.
SILVER CHLORIDE
Identify the acid and the alkali used to prepare sodium nitrate
Acid: Nitric acid
Alkali: Sodium hydroxide
What steps should she now take to obtain dry crystals of sodium nitrate?
- Leave it to dry/ Leave it to warm up in a oven
- Filter
Give the formula of the compound formed when magnesium reacts with steam
MgO
Why is there no temperature rise when silver is added to copper(II) sulfate solution?
Silver is less reactive than copper
Suggest why students did not use calcium metal in their experiments
Calcium would react with water
Describe how to use the method of crystallization to obtain a pure dry sample of the salt from this mixture - volumes of aqueous ammonia and phosphoric acid. (3)
- Boil to produce a concentrated solution
- Leave the solution to cool so that crystals form
- filter to obtain crystals
