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Chapter 9

Chapter 9. Families of Chemical Compounds – Acids & Bases. Flashback – What’s a Chemical Compound?. As we have learned, when elements bond together due to ionic or covalent bonding, they form chemical compounds . Different combinations of elements form different compounds.

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Chapter 9

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  1. Chapter 9 Families of Chemical Compounds – Acids & Bases

  2. Flashback – What’s a Chemical Compound? • As we have learned, when elements bond together due to ionic or covalent bonding, they form chemical compounds. • Different combinations of elements form different compounds. • 2 of these types of compounds are acids and bases.

  3. Properties of Acids • Sour tasting • Affect indicator colors • blue litmus paper turns red • phenolphthalein remains colorless • Acids react with active metals to form Hydrogen gas plus a metal compound

  4. Properties of Acids • When acids are dissolved in water, they produce positive hydrogen ions (H+) (this is a proton) • Acids are often known as proton donors • strong acids dissolved in water produce a lot of hydrogen ions and are good electrolytes – this means that they will conduct electricity very well ex – sulfuric acid, hydrochloric acid • weak acids dissolved in water do not produce a lot of hydrogen ions and are not good electrolytes ex - acetic acid (vinegar)

  5. Properties of Bases • Bitter taste • Slippery – ex soap • Affect indicator colors • red litmus paper turns blue • phenolphthalein turns bright pink • Emulsify (dissolve) fats and oils • This is why we use bases as soap, they dissolve dirt and oils that are on our body) • This is why cleaners often contain ammonia, the cleaner will “cut” through grease and we can wipe it away.

  6. Properties of Bases • Usually contain OH- ion • Why are bases called proton acceptors? • their OH- ions combine with H+ ions (protons from acids) to form water • Common bases • sodium hydroxide (NaOH) • potassium hydroxide (KOH) • Ammonia • Lye • Soap • Milk of magnesia

  7. Common Household Acids and Bases

  8. The pH Scale • The name, pH, has been reported to come from a variety of places including: pondus hydrogenii (Latin), pouvoir hydrogène (French) and potential of hydrogen (English). • However pH is actually a shorthand for its mathematical definition, in chemistry a small p is used in place of writing − log10 and the H should more correctly be [H+], standing for concentration of hydrogen ions • Simply put - the pH of a solution is a measure of the amount of its H+ ion. • Remember that the H+ ion is what is formed when an acid is dissolved into water.

  9. The pH Scale • SO, the pH of a solution is actually a measure of how acidic it is. • But, the scale is a reverse scale, so the lower the number, the higher the acidity.

  10. The pH Scale • the range is from 0 to 14 • What is a solution like if... • its pH is below 7? • its pH is 7? • its pH is above 7? acidic neutral basic

  11. When Acids & Bases Combine… • Formation of Salts • When acids react chemically with bases, they neutralize each other AND form a type of compound called salts. • water – the compound formed from the positive H ion of an acid and the negative OH ion of a base • salt – the compound formed from the negative ion of an acid and the positive ion of a base. • neutralization - acid and base react to form a salt & water. It is a type of double replacement reaction. Oxi #’s +1 -1 +1 -1 +1 -1 HCl + NaOH  NaCl + H2O “Hydrochloric Acid plus Sodium Hydroxide yields Sodium Chloride and Water”

  12. When Acids & Bases Combine… • How to Calculate a Neutralization Reaction • the acid’s H’s and the base’s OH’smust be the same # • use coefficients if you need to • These will combine to form the water (H2O) • put together the leftover parts to make the salt(base part 1st) • don’t multiply subscripts, instead wrap the part in parentheses and put the needed subscript outside • Ex #1: HCl + KOH • 1 H and 1 OH cancel • this leaves a Cl and a K • thus, the salt produced is KCl

  13. Ex #2: H2SO4 + NaOH • 2 H’s but only 1 OH, so you have to put a 2 in front of the the NaOH so that you have enough OH’s to “hook up” with the H’s to make water (H2O) • this leaves SO4 and 2 Na • thus, the salt produced is Na2SO4 • (base part first, acid part second) • What salt is made from each of the following neutralizations? • HNO3 and NaOH • LiOH and HBr • H2SO4 and KOH • HCl and Al(OH)3

  14. Neutralize these or I’ll whine. • Complete the following neutralization reactions. • Circle the acid, Square the base, & Triangle the salt. • LiOH + HBr --> • HCl + FrOH --> • H2SO4 + KOH --> • Ca(OH)2 + HF --> • H2SO4 + Al(OH)3 -->

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