this is for a chemistry laboratory experiment called "how much caffeine is there in instant coffee"
What should be the pH of the aqueous layer to extract caffeine? There are three aqueous solutions that you may choose from.
A. pH >14, using 2.5 M NaOH (aq)
B. pH 1, using 0.1 M HCl (aq)
C. pH 6.2, using 0.1 M NaHCO3 (aq)
note: caffeine does not gain or lose protons in aqueous solution at these pH values
To extract caffeine from instant coffee, you need to consider the solubility of caffeine in different pH environments. Caffeine is more soluble in basic solutions, so you want to choose an aqueous solution with a high pH.
Looking at the options provided:
A. pH >14, using 2.5 M NaOH (aq) - This option has a very high pH, which is ideal for extracting caffeine. However, the concentration of sodium hydroxide (NaOH) is quite strong (2.5 M), which may lead to safety concerns and aggressive reactions.
B. pH 1, using 0.1 M HCl (aq) - This option has a very low pH, which is not suitable for extracting caffeine. Caffeine is not soluble in strongly acidic solutions.
C. pH 6.2, using 0.1 M NaHCO3 (aq) - This option has a pH of 6.2, which is close to neutral. Although caffeine does not gain or lose protons at this pH, it is less soluble compared to higher pH values. Therefore, this option may not be as effective in extracting caffeine as the first option (A).
So, the best choice from the given options to extract caffeine from instant coffee would be option A with pH >14 and using 2.5 M NaOH (aq). However, it is important to note that working with such a strong base requires careful handling and safety precautions.