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The pH Scale

The pH Scale. The ph scale runs from 1-14 and can be regarded as a measure of H + ions present in the solution. 1 2 3 4 5 6. 8 9 10 11 12 13 14. 7. Acids. Alkalis. N e u t r a l. All acids contain H + ions eg. H + Cl - , H 2 + SO 4 2 - and H + NO 3 -.

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The pH Scale

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  1. The pH Scale • The ph scale runs from 1-14 and can be regarded as a measure of H+ions present in the solution 1 2 3 4 5 6 8 9 10 11 12 13 14 7 Acids Alkalis N e u t r a l All acids contain H+ ions eg. H+Cl- , H2+SO42-and H+NO3- All Alkalis contain OH- ions eg.Na+OH-, K+OH- and Ca2+(OH-)2 Strong Alkalis have pH greater than 10. Weak Alkalis have a pH of 8 or 9. Strong Acids have a pH of 1or2. Weak acids have a pH of 3,4,5,6.

  2. Making Acid and Alkalis Acids Acids can be made by heating Non-Metals and dissolving the the resultant non-metal oxide in water Alkalis Alkalis can be made by heating Na, K, Ca and Mg metals and dissolving the resultant oxide in water. Less active Metal Oxides don’t dissolve in water. Carbon Dioxide Sodium oxide Carbon + Oxygen Sodium + Oxygen C + O2 CO2 Na + O2 (Na)2O Carbon Dioxide Carbonic Acid Sodium Oxide Sodium Hydroxide Water + Water + CO2 + H2O H2CO3 (Na)2O + H2O NaOH Acid Alkali

  3. When we dilute an Alkali we keep the number of H+ ions the same although there is a larger volume and therefore the ph also rises Dilution of Acids An acid of a certain Concentration contains a certain amount of H+ ions. When we dilute it i.e. add more water the number of H+ ions remain the same although the volume increases, making it less Concentrated and therefore the pH rises H+ H+ H+ H+ H+ H+ H+ H+ H+ H+

  4. The Mole • Calculations involving the Mole can be seen in the “Calculations in Chemistry” presentation

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