posted by Rachel on .
28: You have a glass of pure water. Are chemical reactions occurring in the water? If so, what are they? If not, explain why not.
29: While investigating the effects of acid rain in your area, you discover a lake that is surprisingly resistant to changes in pH caused by acid rain. Using what you have learned in this unit, explain why the lake resists changes in pH.
41, Information: Hydrochloric acid (HCI) is a relatively strong acid. Imagine that HCI is added to a buffer solution containing the weak acid phosphoric acid (H3PO4) and a salt (Na2HPO4). Answer the following questions.
41, A: Will HCI react to the weak acid (H3PO4), or will it react with the salt (Na2HPO4).?
41, B: One product of this reaction will be a new salt (NaCl). What will the other product be?
28: Yes, because the reaction for water is reversible, so some atoms are evaporating and others are recombining to form water molecules maintaining a balance in the solution.
29: The lake may act as a buffer and either be composed of a weak acid and its conjugate base or vice versa and therefore resists changes in the pH.
41, A: It will react with the salt (Na2HPO4).
41, B: I'm not positive of what they mean?
The answer to 28 is pure garbage. Evaporation of water is a physical process and not a chemical one. And if you leavae the glass of water uncovered, the water will completely evaporate and you will not maintain the balance. Water goes undergo autoioniation as follows:
H2O + H2O ==> H3O^+ + OH^- and that is an ongoing chemical process at work continuously.
29. This answer looks ok.
41A. This answer looks ok.
41B. They mean that if HCl will react with the salt, what are the products? They tell you one of the products is NaCl. They want you to tall what the other product is.
HCl + Na2HPO4 ==> NaCl + ??