Properties+of+acids+and+bases

//** ACIDS **//

//They have several characteristic reactions: //  H 2 SO 4  (aq) + Mg (s) ---> MgSO 4  (aq) + H 2  (g)  2HNO 3  (aq) + CuO (s) ---> Cu(NO 3 ) 2 (aq) + H 2 O (l)  H 3 PO 4 (aq) + 3NaOH (aq) ---> Na 3 PO 4  (aq) + 3H 2 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">O (l) <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Acids react with indicators, thus causing the indicator to change colour. Indicators are substances that change colour when the concentration of H + <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> ions changes. They usually indicate whether a substance is acidic or basic. <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">A universal indicator is a mixture of different indicators that gives a range of colours according to the hydrogen ion concentration.
 * <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Acids have a pH less than 7.
 * <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Acids react with metals which are above hydrogen in the reactivity series to form //salt and hydrogen gas.//
 * <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Acids react with bases (metal oxides and metal hydroxides) to form salt and water. (These are usually known as neutralization reactions)


 * // BASES //**

//<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">A base can simply be defined as a substance that neutralises and acid. A base that is __soluble in water__ is known as an __alkali__. // <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> CaO (s) + 2HCl (aq) ---> CaCl 2 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> (aq) + H 2 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">O (l) <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> NH 4 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Cl (s) + NaOH (ag) ---> NaCl (s) + H 2 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">O (l) + NH 3 <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> (aq) <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Insoluble bases do not react with indicators since they don’t dissolve in water. Since indicators measure the concentration of H + <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> ions, only alkalis (which produce OH - <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> in water) react with and change the colour of indicators.
 * <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Bases have a pH greater than 7.
 * <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Bases neutralise acids to form salt and water.
 * <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Displacement of ammonia from ammonium salts.

By the end of this lesson you should be able to:
 * Outline the characteristic properties of acids and bases in aqueous solutions


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