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The pK a value of hydrochloric acid in aqueous solution is estimated theoretically to be −5.9. [5] A solution of hydrogen chloride in water behaves as a strong acid: the concentration of HCl molecules is effectively zero.
The first step (called SC-1, where SC stands for Standard Clean) is performed with a solution of (ratios may vary) [2] 5 parts of deionized water; 1 part of ammonia water, (29% by weight of NH 3) 1 part of aqueous H 2 O 2 (hydrogen peroxide, 30%) at 75 or 80 °C [1] typically for 10 minutes. This base-peroxide mixture removes organic residues.
The compound hydrogen chloride has the chemical formula HCl and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride gas and hydrochloric acid are important in technology and industry.
A typical mixture is 3 parts of concentrated sulfuric acid and 1 part of 30 wt. % hydrogen peroxide solution; [1] other protocols may use a 4:1 or even 7:1 mixture. A closely related mixture, sometimes called "base piranha", is a 5:1:1 mixture of water, ammonia solution ( NH 4 OH , or NH 3 (aq) ), and 30% hydrogen peroxide.
A more convenient laboratory method involves the (reversible) dehydration of nitrous acid by HCl [4] HNO 2 + HCl → H 2 O + NOCl. By the direct combination of chlorine and nitric oxide; This reaction reverses above 100 °C. Cl 2 + 2 NO → 2 NOCl. By reduction of nitrogen dioxide with hydrogen chloride: [5] 2NO 2 + 4 HCl → 2NOCl + 2H 2 O + Cl 2
McIlvaine buffer is a buffer solution composed of citric acid and disodium hydrogen phosphate, also known as citrate-phosphate buffer.It was introduced in 1921 by the United States agronomist Theodore Clinton McIlvaine (1875–1959) from West Virginia University, and it can be prepared in pH 2.2 to 8 by mixing two stock solutions.
3 + 4 HCl [AuCl 4] − + NO + H 3 O + + H 2 O. Solid tetrachloroauric acid may be isolated by evaporating the excess aqua regia, and decomposing the residual nitric acid by repeatedly heating the solution with additional hydrochloric acid. That step reduces nitric acid (see decomposition of aqua regia).
A weak acid cannot always be neutralized by a weak base, and vice versa. However, for the neutralization of benzoic acid (K a,A = 6.5 × 10 −5) with ammonia (K a,B = 5.6 × 10 −10 for ammonium), K = 1.2 × 10 5 >> 1, and more than 99% of the benzoic acid is converted to benzoate.