Acids, Bases and Salts Critical Essay

All substances are divided into three categories: Acidic Alkaline Neutral How can this be measured? We usually do this by measuring the pH of the substance. What the pH is that its simply measure of the Hydrogen ion concentration in a substance. However, calculations of that is beyond the scope of the IGCSE Science - if you do, however, want to get a feel of pH calculations, you can visit here. pH 1-6 substances are usually acidic pH 7 substances are usually neutral pH 7-14 substances are usually alkaline

This is a substance that changes color when it is added to another substance. What color it changes to depends on the pH of the substance.

This is an indicator also used to test for acidity, neutrality or alkalinity in a substance. We use something called litmus paper to test for this. If we want to test for acidity, we use Blue Litmus Paper If we want to test for alkalinity, we use Red Litmus Paper The following results are: Acids: Turn blue litmus paper red. Alkalines/Bases: Turn red litmus paper blue. Neutral: No color change.

Metal + Acid ? Salt + Hydrogen We call this the "Displacement" method. Bubbles are given out Temperature rises (the reaction is exothermic, heat is released) Metal disappears

We call this the Neutralization Method. Without fail, water is produced as a product in a neutralization reaction. There are two types of "Neutralization" reactions. 1) Acid + Metal Oxide ? Salt + Water Copper Oxide + Sulfuric Acid ? Copper Sulfate + Water Here, the Copper merges with Sulfuric acid to make Copper sulfate. If you have iron oxide, nothing will change, the iron will merge with the sulfuric acid to make copper sulfate. 2) Acid + Metal Hydroxide ? Salt + Water Hydrochloric Acid + Sodium Hydroxide ? Water + Sodium Chloride

E.g. Sulfuric Acid (Acid) + Copper Carbonate (Carbonate) ? Copper sulfate (salt) + Water + Carbon Dioxide Metal carbonate starts to disappear Temperature rises (exothermic reaction) Color Change

Most crops grow best when the pH of the soil is near 7. If soil is too acidic or too alkaline, crops grow badly or not at all. Usually acidity is the problem. Why? Because of a lot of vegetation rotting in it or because too much fertilizer was used in the past. To reduce the acidity, the soil is treated with a base like limestone or quicklime or slaked lime. Affects of lower pH: Lack of nutrients Poor growth of crops May pass onto rivers, damaging the eco-system within it.

Oxides are compounds composed of oxygen and another element.

Copper (II) oxide is called a basic oxide since it can neutralize an acid: Base + Acid —> Salt + Water CuO (s) + 2HCl (aq) —> CuCl2 (aq) + H2O (l) Iron (III) Oxide and magnesium also behaves in a similar way- they also neutralize acids, and therefore they are basic oxides. Generally, metals react with oxygen to form basic oxides.

Carbon Dioxide is slightly soluble in water as the solution will turn litmus paper red, which makes Carbon Dioxide acidic. CO2 + H2O —> H2CO3 Sulfur dioxide and phosphorus pentoxide also dissolve in water to form acids, so therefore, they are also acidic oxides. Generally, non-metals react with oxygen to form acidic oxides.

Some oxides of non-metals are neither acidic nor basic. These are called neutral oxides. Neutral oxides neither react with acids or bases. Examples Include: Carbon Monoxide Dinitrogen Oxide

Take the acid and: Warm it Add the base Let the acid and the base react. Filter out solution Evaporate water from produced during reaction Retrieve Salt E.g. HCl + NaOH ? NaCl + H2O NaCl is a Salt.

Separating a mixture is quite easy, as they are not chemically fused together. For example, we can easily separate salt and sand as they are not chemically combined together. The procedure to separating them are as follows: Add water Stir Wait for the salt to dissolve Filter the mixture. Most of the sand will be trapped in the filter, but the salt will pass through. Rinse the sand in water. Dry it in an oven. Evaporate water from salt solution to produce dry salt.

If Salt is soluble, distillation. If Salt is insoluble, filtration. We just described filtration, so we'll talk a little bit about distillation. The steps in distillation: Gently heat the solution in the flask. As the temperature increases, the liquids will eventually boil, allowing the water vapour the slowly rise to the condenser, leaving the salt behind. Vapour condenses to water in the condenser, and the water falls into a beaker through the condenser.

Ammonium, copper(II), iron(II), iron(III) and zinc by means of aqueous sodium hydroxide and aqueous ammonia as appropriate. Ammonium (NH4+) Add dilute sodium hydroxide, and then heat gently. Damp red litmus paper turns blue and ammonia gas is released. Copper (II) Add dilute sodium hydroxide OR ammonia solution Pale blue precipitate forms.However, as you add more ammonia, the solution dissolves, leading to a deep blue solution. Iron (II) Add dilute sodium hydroxide OR ammonia solution. Pale green precipitate forms. Iron (III) Add dilute sodium hydroxide OR ammonia solution. Red-brown precipitate forms. Zinc Add dilute sodium hydroxide OR ammonia solution White precipitate forms.

- Carbonate by means of dilute acid and then limewater, - Chloride by means of aqueous silver nitrate under acidic conditions, - Nitrate by reduction with aluminium, - Sulfate by means of aqueous barium ions under acidic conditions, Carbonate Add dilute hydrochloric acid Anion is present if bubbles give off gas that turns limewater milky Chloride Add same amount of nitric acid as the chloride Add silver nitrate solution Chloride ions will form a white precipitate. Nitrate Add sodium hydroxide.Afterwards, add some pieces of aluminium Nitrate ions are present if ammonia gas is given off. Sulfate Add same amount of dilute hydrochloric acid.Next, add Barium Nitrate solution. White precipitate will form if Sulfate ions are present.

- Ammonia by means of damp red litmus paper, - Carbon dioxide by means of limewater, - Chlorine by means of damp litmus paper, - Hydrogen by means of a lighted splint, - Oxygen by means of a glowing splint. Ammonia, NH3 Use damp red litmus paper Indicator turns blue Carbon Dioxide, CO2 Bubble the suspected Carbon Dioxide sample through limewater. Limewater becomes cloudy or milky. Chlorine, Cl2 Hold damp litmus paper in the gas. Paper turns white. Hydrogen, H2 Put the gas in the tube and hold a lighted splint into the tube. Gas burns with a squeaky pop Oxygen, O2 Collect the gas in a test tube and hold a glowing splint next to it. Splint relights.