Ethanoate, sodium

The sodium ethanoate which is largely dissociated, serves as a source of ethanoate ions, which combine with any hydrogen ions which may be added to the solution to yield more of the acid. The addition of hydrogen ions has therefore much less effect on such a solution than it would have on water. In a similar manner, the solution of the salt of a strong acid and a weak base, in the presence of a weak base, has a pH that is insensitive to additions of alkali. 

Cr(02CCH3)2]2,2H20. Red insoluble compound formed from sodium ethanoate and CrC)2 in aqueous solution. The most stable Cr(II) compound contains a Cr —Cr bond, chromium fluorides... 

Prepared by healing benzaldehyde with sodium ethanoate and ethanoic anhydride (Perkin reaction) or with ethyl ethanoate and sodium ethoxide. Occurs in storax, or liquid... 

K2 is called the hydrolysis constant for sodium ethanoate. Hydrolysis occurs when salts involving weak acids or bases are dissolved in water. It is often also found with metal ions in solution. The ion [M(H20) ] dissociates to the hydroxy species [M(H20) , (OH)]f 1. ... 

Perkin reaction A condensation between aromatic aldehydes and the sodium salts of fatty acids or their aromatic derivatives. The reaction between benzaldehyde and sodium ethanoate in the presence of ethanoic anhydride leads to sodium cinnamate... 

C7H9N402- M.p. 337 C, an alkaloid obtained from cacao seeds or prepared synthetically. Constitutionally it is similar to caffeine, and is also a weak base. It is usually administered as the sodium compound combined with either sodium ethanoate or sodium salicylate, and is employed almost entirely as a diuretic. Physiologically theobromine resembles caffeine, but its effect on the central nervous system is less, while its action on the kidneys, is more pronounced. 

For example, a buffering solution can be made from ethanoic acid (CH3COOH) and its salt sodium ethanoate (CH3COONa). Sodium ethanoate completely ionizes in water to form sodium ions and ethanoate ions ... 

CHjCOONa (aq) - Na+(aq) + CH3COO (aq) sodium ethanoate sodium ion ethanoate ion... 

To make a buffering solution, ethanoic acid is added to the dissolved sodium ethanoate. Because the ethanoic acid is a weak acid, it does not ionize completely. However, it does release hydrogen ions, some of which react with the ethanoate ions to form more ethanoic acid. The solution now contains a lot of ethanoate ions and enough hydrogen ions to make it acidic. 

But we need to be careful when talking about the magnitudes of Consider the case of sodium ethanoate dissolved in dilute mineral acid the reaction occurring is, in fact, the reverse of that in Equation (4.45), with a proton and carboxylate anion associating to form undissociated acid. In this case, = 1 mol before the reaction occurs, and its value decreases as the reaction proceeds. In other words, we need to define our reaction before we can speak knowledgeably about it. We can now rewrite our question, asking Why is < 1 for a weak acid ... 

Worked Example 6.13 Consider the so-called acetate buffer , made with equal volumes of sodium ethanoate and ethanoic acid solutions. The concentration of each solution is 0.1 mol dm-3. A small volume (10 cm3) of strong acid (HC1 of concentration 1 mol dm 3) is added to a litre of this buffer. The pH before adding HC1 is 4.70. What is its new pH ... 

Examples of salts from weak acids and strong bases include sodium ethanoate and potassium carbonate. 

Consider a solution of sodium ethanoate, Na+CHjCOO". This is the salt of the weak acid, ethanoic acid, and the strong base, sodium hydroxide. Again, the equilibrium present in water is ... 

In solution, sodium ethanoate is alkaline and so contains more OH" ions than H ions. This means that some of the H+ ions present in the water equilibrium must have been removed. 

The negative CH3COO" ions present in sodium ethanoate react with the positive H ions to form ethanoic acid molecules. This happens because ethanoic acid is a weak acid and, in the equilibrium equation, the position of equilibrium lies well over to the right-hand side, so there will be mainly aqueous ethanoic acid molecules and fewer ions. 

An acid buffer consists of a solution of a weak acid and one of its salts. An example of an acid buffer is a solution of ethanoic acid and sodium ethanoate. Sodium ethanoate is an ionic salt and, although the sodium ions are just spectator ions, the ethanoate ions are the conjugate base of ethanoic acid. Ethanoic acid is a weak acid and is only partially dissociated ... 

Using information from pp. 4 and 13 in the SQA Data Booklet, calculate the pH of the buffer solution made when 40 cm of 01 mol 1" ethanolc acid solution is mixed with 60 cm of 01 mol 1" sodium ethanoate solution. 

When an alkali, say sodium hydroxide, is used as a catalyst, this helps to drive the equilibrium position to the side of the products. The reason is that the sodium hydroxide reacts with the ethanoic acid to form sodium ethanoate. Ethanoic acid, however, is easily generated from the sodium ethanoate by adding a strong acid such as hydrochloric acid. 

To obtain this result, remember that 40 cm of 0-1 mol 1 ethanoic acid solution diluted to a total volume of 100 cm becomes 0-04 mol 1 and that 60 cm of 0-1 mol 1 sodium ethanoate solution diluted to a total volume of 100 cm becomes 0-06 mol F. ... 

When 1.00 mol of sodium ethanoate (NaOAc) is dissolved in 1.00 dm3 of water, Na+ ions are liberated and some of the AcO-species combine with H30+ to form ethanoic acid (AcOH). The following equilibria are set up ... 

Suppose a water solution was made up initially to be 0.01 M in methyl bromide and 1.0M in sodium ethanoate at 50°. In water, the SN2 rate constant for reaction of hydroxide ion with methyl bromide at 50° is 30 X 10-4 liter mole-1 sec-1, whereas that of ethanoate ion at 50° is 1.0 x 10-4 liter mole-1 sec-1. The ionization constant of ethanoic acid at 50° is 1.8 x 10-5. In the following, neglect the rates of the reactions of methyl bromide with water or ethanoic acid and any further reactions of ethanoate ... 

Ethanoic acid Ethanoates Sodium ethanoate (CH3COONa)... 

Methanoic acid is present in stinging nettles and ant stings. Ethanoic acid, however, is the most well known as it is the main constituent of vinegar. Like other acids, ethanoic acid affects indicators and will react with metals such as magnesium. However, whereas the mineral acids such as hydrochloric acid are called strong acids, ethanoic acid is a weak acid (Chapter 8, p. 120). Even though it is a weak acid, it will still react with bases to form salts. For example, the salt sodium ethanoate is formed when ethanoic acid reacts with dilute sodium hydroxide. 

Sodium acetate (sodium ethanoate) A salt of acetic acid. 

Like all acids, the carboxylic acids will form salts with alkalis. With sodium hydroxide ethanoic acid will form sodium ethanoate (or sodium acetate). Salts of... 

Sodium ethanoate is an ionic compound it is completely dissociated... 

When a small amount of a strong acid is added is added to the solution containing the buffer, there is an excess of H+ ions which upsets the position of the equilibrium in (1) and, in accordance with Le Chatelier s Principle, causes a shift to the left in order to remove those ions. A weak acid such as ethanoic can only remove so many H" ions by shifting its equilibrium position the addition of an ionic salt to a buffer solution, in this case sodium ethanoate (2), produces many more ethanoate ions which can then combine with any excess H+ ions [not removed by (1)]. This forms the weak ethanoic add, and so restores the pH of the solution. 

Acetic acid, sodium salt E262 sodium ethanoate. 

In effect, the term buffer capacity means the range of pH over which a buffer is effective. The commonly held view is that this range lies within p T 1- The table and graph below illustrate the buffering capacity of the ethanoic acid/sodium ethanoate buffer, and allow a judgement to be made as to whether the accepted range, 1, is reasonable. pK for ethanoic acid is 4.76 at 25°C. 

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