Date of publication: 2017-09-02 18:51
The salt of a weak acid and strong base will form an alkaline [ alkali : A base which is soluble in water. ] solution when dissolved in water.
To measure the hydrogen gas released in the above reaction we use the apparatus as shown. As the bubbles of gas are given off, the plunger in the syringe moves out as hydrogen gas fills it. After, say every 75 seconds we read the volume of gas in the syringe. The reaction is complete when the syringe no longer moves.
A piece of cotton wool is placed in the neck of the flask to allow carbon dioxide gas to escape. As the gas escapes the mass of the flask reduces. Take readings of mass loss over a time interval, . 85 seconds.
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Concentration affects the rate of reaction. Therefore over time as the concentration of HCl increased then the rate of the reaction also increased.
What we observe over time is that gradually the zinc disappears and bubbles of gas appear. After a few minutes the bubbles of gas form less and less quickly until finally no bubbles appear because all the acid has been used up, some zinc remains.
The rate of reaction was determined by measuring the time required for a given amount of magnesium metal to be consumed by Hydrochloric acid (HCl) solution of varying concentrations.
The equal proportions of hydrogen ions and hydroxide ions in the solution are not disturbed by additional equilibria, and so the pH of the solution is equal to 7.
Magnesium ribbon , ruler, scissors, analytical balance, sandpaper, hydrochloric acid, measuring cylinder, graduated cylinder, distilled water, glass stirring rod.
This additional equilibrium removes hydrogen ions, but not hydroxide ions. The water equilibrium shifts to the right, to replace these lost hydrogen ions and, in so doing, also produces more hydroxide ions. There are now more hydroxide ions than hydrogen ions present, leading to a pH of more than 7.
The rate of a chemical reaction is the time required for a given quantity of reactant(s) to be changed to product(s). The unit of time may be seconds, minutes, hours, days or years.
Soaps are also salts of weak acids (such as stearic and oleic acid) and strong bases (such as sodium and potassium hydroxide). As a result, soaps are usually alkaline in nature.