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Acids and Bases

Acids and Bases. Pagal and Closas. Properties of Acids and Bases. *Physical behavior of Acids - taste sour *Physical behavior of Bases - taste bitter - feel slippery. Properties of Acids and Bases. *Chemical behavior of Acids

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Acids and Bases

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  1. Acids and Bases Pagal and Closas

  2. Properties of Acids and Bases *Physical behavior of Acids - taste sour *Physical behavior of Bases - taste bitter - feel slippery

  3. Properties of Acids and Bases *Chemical behavior of Acids - Acids release a hydrogen ion into water (aqueous) solution. + By the 1884 definition of Svante Arrhenius (Sweden), an acid is a material that can release hydrogen ion (H+). Hydrogen chloride in water solution ionizes and becomes hydrogen ions and chloride ions.  - Acids neutralize bases in a neutralization reaction. + An acid and a base combine to make a salt and water. A salt is any ionic compound that could be made with the anion of an acid and the cation of a base. The hydrogen ion of the acid and the hydroxide ion of the base unite to form water.

  4. Properties of Acids and Bases - Acids corrode active metals + When an acid reacts with a metal, it produces a compound with the cation of the metal and the anion of the acid and hydrogen gas. - Acids turn blue litmus to red. + Litmus is one of a large number of organic compounds that change colors when a solution changes acidity at a particular point. Litmus is the oldest known pH indicator. It is red in acid and blue in base. Litmus does not change color exactly at the neutral point between acid and base, but very close to it. Litmus is often impregnated onto paper to make 'litmus paper.'

  5. Properties of Acids and Bases - Acids can accept a pair of electrons + proposed by Lewis on his Lewis theory that states, electrons and not the protons are the ones transferring -Acids are substances from which a proton can be removed + Lowry-Bronsted Theory; proposed that hydrogen ions cannot exist in water but rather covalently bond with water

  6. Properties of Acids and Bases *Chemical behavior of Bases - Bases release a hydroxide ion into water solution + If that is the case, a base, or alkali, is a material that can donate a hydroxide ion (OH-). Sodium hydroxide in water solution becomes sodium ions and hydroxide ions. - Bases neutralize acids in a neutralization reaction. + The word - reaction is: Acid plus base makes water plus a salt. Where 'Y' is the anion of acid 'HY,' and 'X' is the cation of base 'XOH,'  and 'XY' is the salt in the product, the reaction is: HY + XOH   HOH + XY

  7. Properties of Acids and Bases - Bases denature protein. + This accounts for the "slippery" feeling on hands when exposed to base. - Bases turn red litmus to blue - Bases can donate a pair of electrons (Lewis Theory) - Bases are substances that bind protons (Bronsted-Lowry Theory)

  8. Differentiating Acids and Bases

  9. Strengths of Acids and Bases Strong Acid: An acid that has a very low pH (0-4). Strong Base: A base that has a very high pH (10-14).  Weak Acid: An acid that only partially ionizes in an aqueous solution. That means not every molecule breaks apart. They usually have a pH close to 7 (3-6).  Weak Base: A base that only partially ionizes in an aqueous solution. That means not every molecule breaks apart. They usually have a pH close to 7 (8-10).  Neutral: A solution that has a pH of 7. It is neither acidic nor basic. 

  10. Quantifying Acids and Bases • It cannot be measured experimentally, so they are based on theoretical calculations. The pH scale is not an absolute scale. • Pure water is said to be neutral, with a pH close to 7.0 at 25 °C (77 °F). • Solutions with a pH less than 7 are said to be acidic. • Solutions with a pH greater than 7 are said to be basic. 

  11. Quantifying Acids and Bases Mathematical definition • pH is defined as minus the decimal logarithm of the hydrogen ion activity in a solution. • pOH is sometimes used as a measure of the concentration of hydroxide ions, OH−, or alkalinity. pOH is not measured independently, but is derived from pH. The concentration of hydroxide ions in water is related to the concentration of hydrogen ions by [OH−] = KW /[H+] where KW is the self-ionization constant of water. Taking cologarithms: pOH = pKW − pH.

  12. pH Indicators An acid-base indicator is a weak acid or base. It is also the measure of the acidity or basicity of a solution. The connected form of a pH indicator has a different color than an iogenic form of the pH indicator. Color change occurs over a range of Hydrogen ion concentrations. This range is called the color change interval.

  13. Common Applications/Uses of Acids and Bases • There are numerous uses of acids: • Acids are often used to remove rust and other corrosion from metals. • They may be used as an electrolyte in a wet cell battery (figure 1), such as sulfuric acid in a car battery.

  14. Common Applications/Uses of Acids and Bases • There are many uses of bases too: • Ammonium hydroxide, or ammonia water, is a base. This is very irritating to the nose and the eyes. It is often used in the home for cleaning because bases generally dissolve grease. • Lye (sodium hydroxide), which is used in the manufacture of soap, is another familiar kind of base.

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