1)Equal lengths of magnesium ribbon are dropped in test tubes A and B.Hydrochloric acid is added to test tube A,while acetic acid is added to test tube B.In which test tube will the fizzing occur more vigorously and why?
2)Fresh milk has a pH of 6.How do you think the pH will change as it turns into curd?Explain your answer.
1) The fizzing will occur more vigorously in test tube A, where hydrochloric acid is added. This is because hydrochloric acid is a stronger acid compared to acetic acid. When magnesium reacts with hydrochloric acid, it forms magnesium chloride and hydrogen gas. The reaction between a stronger acid and magnesium will be more vigorous, resulting in a more intense fizzing.
2) The pH will decrease as milk turns into curd. Curdling of milk occurs when the proteins in milk coagulate, forming solid curds and liquid whey. During this process, lactic acid bacteria ferment the lactose present in milk, producing lactic acid. Lactic acid is a weak acid, and its production leads to a decrease in pH. Therefore, as milk turns into curd, the pH will decrease from its initial value of 6.
1) The fizzing or vigorous reaction will occur more in test tube A, where hydrochloric acid is added to the magnesium ribbon. This is because hydrochloric acid is a stronger acid than acetic acid. It ionizes completely in water and releases a higher concentration of hydrogen ions (H+), which react with the magnesium ribbon to produce hydrogen gas (H2). This reaction is more vigorous and results in a faster release of gas.
On the other hand, acetic acid is a weaker acid and does not ionize completely in water. It releases a lower concentration of hydrogen ions compared to hydrochloric acid. Therefore, the reaction between acetic acid and magnesium ribbon will be less vigorous, resulting in a slower release of gas.
2) As fresh milk turns into curd, the pH will decrease. This is because the curdling of milk is caused by the process of fermentation, where lactose (milk sugar) is converted into lactic acid by the presence of bacterial cultures. Lactic acid is a stronger acid than the neutral pH of milk, around 6.
When lactic acid is produced during fermentation, it decreases the pH of the milk. The increase in acidity gives the characteristic sour taste of curd and also helps in the coagulation of proteins, resulting in the formation of curd. So, the conversion of milk into curd leads to a decrease in pH due to the formation of lactic acid.