3 1 acids

The ion that causes a substance to be acidic is a hydrogen ion / H+.

The ion that causes a substance to be alkaline is a hydroxide ion / OH-.

pH 7 is classed as neutral.

The pH range for alkaline is 8-14.

The pH range for an acid is 0-6.

Litmus is red in acid and blue in alkaline conditions.

Phenolphthalein is colourless in acid.

Methyl orange is red in acid and yellow in alkaline conditions.

To measure the pH of a substance with universal indicator: (Universal indicator paper can also be used).

Universal indicator is not used for titrations as it does not give a sharp colour change which is required to identify the end-point.

The pH scale goes from pH 0 - 14.

True. The higher the concentration of hydrogen ions, the lower the pH.

True. The higher the concentration of hydroxide ions in solution, the higher the pH.

If the pH increases by 1, the concentration of hydrogen ions increases by a factor of 10.

A strong acid will have more hydrogen ions in solution than a weak acid of equal concentration.

True. The lower the pH, the more acidic the solution is.

The concentration of hydrogen ions in a solution of pH 4 is 100 times (10 x 10) greater than a solution with a pH of 6.

The pH of distilled water is 7.

The new pH is 2. If the hydrogen ion concentration increases by a factor of 10 by the pH decreases by 1. So increase by a factor of 1000 will decrease the pH from 5 to 2.

A strong acid is an acid that completely dissociates in water, producing a high concentration of H+ ions.

Hydrochloric acid (HCl), sulfuric acid (H2SO4) and nitric acid (HNO3) are examples of strong acids.

True. Weak acids have a pH between 4-6.

A solute is a substance that is dissolved in a solvent to form a solution.

A solvent is a substance, typically a liquid, that dissolves a solute to form a solution.

True. A dilute strong acid can have a lower pH than a concentrated weak acid due to complete dissociation.

The ⇌ symbol indicates that the acid is weak, an equilibrium is established and the acid only partially dissociates.

A concentrated solution contains a large amount of solute in a given volume of solution.

A dilute solution contains a small amount of solute in a given volume of solution.

A strong acid dissociates completely in water, while a weak acid only partially dissociates.

A base that is water-soluble is referred to as an alkali. All alkalis are bases, but not all bases are alkalis.

Alkalis have pH values above 7.

Bases are usually oxides, hydroxides, or carbonates of metals.

When ammonia reacts with water, it produces hydroxide ions.

In basic (alkaline) conditions, red litmus paper turns blue.

True. Aqueous ammonia and ammonium hydroxide are the same thing.

The hydroxide, OH-, ion is produced in alkaline solutions.

The general equation for the reaction between a base and acid is: acid + base ⟶ salt + water

The type of reaction is neutralisation.

The general equation for the reaction between a metal and acid is: metal + acid ⟶ salt + hydrogen

False. Only metals above hydrogen in the reactivity series will react with dilute acids.

The general equation for the reaction between an acid and a base is: acid + base ⟶ salt + water

A neutralisation reaction is a reaction between an acid and a base to form a salt and water.

False. Effervescence is produced when an acid reacts with a metal carbonate, due to the formation of carbon dioxide gas.

The products formed from the reaction between sodium hydroxide and hydrochloric acid are sodium chloride and water.

The general equation for the reaction of a metal carbonate with an acid is: metal carbonate + acid ⟶ salt + carbon dioxide + water

The word equation for the reaction between sodium carbonate and sulfuric acid is: sodium carbonate + sulfuric acid ⟶ sodium sulfate + water + carbon dioxide

The identity of the salt produced depends on the acid used and the positive ions in the base.

Metal oxides, metal hydroxides and metal carbonates act as bases in acid-base reactions.

The test and result for hydrogen gas is that a burning splint gives a squeaky pop sound.

The test and result for carbon dioxide gas is that a limewater turns cloudy.

The chemical name for limewater is calcium hydroxide.

The formula of carbon dioxide is CO2.

It is hard to identify these gases as they are colourless and odourless.

The method used to prepare a soluble salt from an acid and alkali is titration.

The piece of equipment which could be used to measure a fixed volume of acid is a pipette.

Phenolphthalein is colourless in acids and pink in alkalis.

The solution is heated gently (until crystals start to form) and then left to cool.

A soluble salt can be made by the reaction of an acid with an alkali

The purpose of adding the indicator is to visually determine when the acid has neutralised the alkali by observing the colour change.

True. The same volume of acid determined from the titration is added again to the same volume of alkali, but without the indicator this time.

An ionic compound consists of a giant lattice of positively charged metal ions and negatively charged non-metal ions.

Insoluble means the substance is unable to dissolve in a solvent, usually water.

False. Not all ionic compounds are soluble in water, some are insoluble.

True. Sodium carbonate is soluble.

True. Compounds of potassium are soluble.

False. Compounds of sodium are soluble.

Three examples of insoluble sulfates are:

False. All nitrates are soluble.

Examples of soluble hydroxides include:

False. Silver chloride is insoluble.

An insoluble salt is a salt that does not dissolve in water or other solvents.

True. Insoluble salts can be prepared using a precipitation reaction.

A precipitation reaction is a reaction where an insoluble solid (precipitate) is formed from two soluble reactants

A precipitate is an insoluble solid that is formed from a reaction between two soluble reactants.

The method for preparing an insoluble salt involves measuring out a fixed volume of one solution and then adding the second salt solution until it is in a slight excess, to ensure the maximum amount of precipitate will be obtained.

False. The precipitate is recovered by filtration and then it must be washed with distilled water to remove reactants that are contaminating the residue (recovered solid).

Examples of salts made by precipitation include silver and lead(II) salts e.g. lead(II) iodide, silver chloride.

The precipitate is washed with distilled water to remove traces of the solutions it was made from.