Acids <br />One important group of chemicals is acids.<br />Some common acids are – Hydrochloric Acid<br />               ...
Acids
Acids
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Acids

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Acids

  1. 1. Acids <br />One important group of chemicals is acids.<br />Some common acids are – Hydrochloric Acid<br />                                                 Sulphuric Acid<br />                                     Nitric Acid<br />                                     Ethanoic Acid<br />Acids are always used in the liquid form in the laboratory.<br />There are many acids present in our everyday lives. Lemon juice contains citric acid, ant and nettle stings contain methanoic acid, tea contains tannic acid and vinegar contains ethanoic acid.<br />You can easily tell if a substance is an acid or not by its’ effect on litmus, litmus is a purple dye which comes in the form of a solution or as strips of red and blue paper. Blue litmus paper is used for testing acids, if the paper or the solution turn red then the substance is an acid. Red litmus paper cannot be used as neutral solutions would keep the paper red aswell as acidic solutions.<br />Acids have many properties that distinguish them from other substances.<br />These are:<br />Acids have a sour taste, e.g. the taste of vinegar ( ethanoic acid)<br />Acids turn litmus solution red and turn blue litmus paper red also<br />Acids have pH numbers less than 7<br />Acids react with metals, forming hydrogen and a salt<br />Acids react with carbonates, forming a salt, water and carbon dioxide<br />Acids react with alkalis, forming a salt and water<br />Acids react with metal oxides, forming salt and water<br />Remember that:<br />The salts of sulphuric acid are known as sulphates <br />The salts of hydrochloric acid are known as chlorides <br />The salts of nitric acid are known as nitrates <br />There are different strengths of acids; some strong acids are hydrochloric acid, sulphuric acid and nitric acid. Some weak acids are ethanoic acid, citric acid and carbonic acid. This is all to do with the number of H+ ions formed in the solution.<br />Alkalis <br />Another important group of chemicals are alkalis.<br />Some common alkalis are – Sodium Hydroxide<br />                                     Potassium Hydroxide<br />                                     Calcium Hydroxide<br />                                     Ammonia<br />These are usually solid s but are used in aqueous solutions in the laboratory.<br />Alkalis are present in many cleaning substances in use in our homes today, especially in kitchen cleaners like oven spray, floor cleaners and creams for sinks. Kitchen cleaners are alkaline because they contain ammonia or sodium hydroxide, which attack grease.<br />You can easily figure out if a substance is alkaline by its’ effect on litmus solution or red litmus paper. Alkalis turn litmus solution blue and red litmus paper blue.<br />Alkalis have many characteristics, which separate them from other chemicals.<br />These are:<br />Alkalis feel soapy to touch<br />Alkalis turn litmus solution blue or turn red litmus paper blue<br />Alkali solutions have pH numbers greater than 7<br />All alkalis ( except ammonia) will react with ammonium compounds<br />All alkalis react with acids<br />There are different strengths of alkalis; this is to do with the formation of OH- ions in the solution. Some strong alkalis are calcium hydroxide, sodium hydroxide and potassium hydroxide. The most recognizable and common weak alkali is ammonia.<br />The pH of Substances, Universal Indicator and Neutral Solutions <br />There are many different strengths of acids and alkalis. The strengths of these are judged using the pH scale. The numbers range from 0 – 14.<br />Click here to see a diagram:<br />An acidic solution has a pH number less than 7, the lower the number the stronger the acid. An alkaline solution has a pH number greater than 7, the higher the number the stronger the alkali. A neutral solution has a pH number of exactly 7.<br />You can find the pH of any solution by using universal indicator. Universal Indicator is a mixture of dyes, like litmus it can be used as a solution or as universal indicator paper. It goes a different colour at different pH values. It ranges from red (a strong acid) to a deep violet (a strong alkali). Universal indicator turns neutral solutions green.<br />Neutral substances are those that are neither acid nor alkali. Some common neutral substances are:<br />Sodium Chloride (common salt)<br />Sugar Solution<br />

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