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Published byBranden Allison Modified over 9 years ago
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Acids & Bases
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What is an Acid? Acids are substances that dissociate (fall apart into ions) in water to form hydrogen ions (H + ). Acids are: –Sour-tasting. –Water-soluble (aqueous). –Very reactive. –Ionic compounds. Acids will usually start with hydrogen at the beginning of their formulas. Common acids include: –Hydrochloric Acid – HCl –Nitric Acid – HNO 3 –Sulfuric Acid – H 2 SO 4 –Citric Acid – HC 6 H 7 O –Acetic Acid – HC 2 H 3 O 2
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What is a Base? Bases are substances that accept the hydrogen ions (H + ) that acids form. Bases, like acids, dissociate in water.Another word for a substance that acts as a base is alkaline. Bases are: –Bitter-tasting. –Water-soluble (aqueous). –Very reactive. –Ionic compounds. Many bases, but not all, will end with the hydroxide ion (OH - ). Common bases include: –Sodium hydroxide – NaOH –Calcium hydroxide – Ca(OH) 2 –Potassium hydroxide - KOH –Ammonium hydroxide – NH 4 OH –Sodium bicarbonate – NaHCO 3
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The pH Scale The pH scale provides chemists with a way of measuring the strength of an acid or base. pH stands for “portenz of hydrogen” – which means “strength of hydrogen”. The pH scale ranges from 0 – 14. A pH value of 7 is right in the middle of this and it represents a perfectly neutral pH – neither acid nor base – like pure water.
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The pH Scale Acids go from 7 to 0 on the pH scale. Acids get more and more stronger as you get closer to 0. Bases go from 7 to 14 on the pH scale. Bases get more and more stronger as you get closer to 14. Each step on the pH scale means you are changing the strength by 10 times.
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Acid-Base Indicators An acid-base indicator is any substance that changes colour in the presence of an acid or a base. Litmus – a plant extract – is the most widely known and used acid-base indicator. Litmus turns red in the presence of acids Litmus turns blue in the presence of bases. Universal indicators show a different colour for many pH values. They often come in the form of pH paper which contains many different acid-base indicators in it.
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Neutralization Reactions A neutralization reaction occurs when an acid and a base undergo a double displacement reaction to form water and a salt (ionic compound). The general equation for a neutralization is: Acid + Base Water + Salt It is called a neutralization reaction because the effects of the acid and the base cancel each other out to make water. Examples: –NaOH + HCl H 2 O + NaCl –H 2 SO 4 + 2KOH 2H 2 O + K 2 SO 4 –H 3 PO 4 + Al(OH) 3 3H 2 O + AlPO 4
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The End…For Now!
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