Which of the following is a base? Which is a Solid?(a) CaSO4 (b) NH4Cl (c) Mg(OH)2 (d) H2O (e) H2O (f) H3PO4?
Answer:
Calcium sulfate (a), ammonium chloride (b), and magnesium hydroxide (c) are all solids at room temperature and pressure when not dissolved in water. Water (d) and (e) can also be a solid, liquid, or gas at room temperature and pressure, though it will not remain a solid when it comes to equilibrium.
(Ortho)phosphoric acid is strange stuff that is nominally solid at room temperature but which has a melting point low enough to become a liquid on a really hot day. Phosphoric acid can also exist in a hydrated form that has an even lower melting point, though still high enough to be solid in a cool room. Or it can deliquesce - pull enough water out of the air to dissolve itself.
Magnesium hydroxide is a strong base which will completely dissociate into its Mg2+ and OH- ions when dissolved in water, or at least that small amount that will dissolve despite magnesium hydroxide's official status as insoluble in water. Pure water is neither an acid nor a base. Phosphoric acid is of course an acid and not a base.
Calcium sulfate solution is very weakly basic. The calcium ions dissociate completely and so do the first of the hydrogen ions from the bisulfate (HSO4-) ions, but the second hydrogen ions don't dissociate completely, leaving some undissociated HSO4- in solution and binding up a fraction of the hydrogen. This leaves a slight excess of OH- in the water, making the solution basic.
In ammonium chloride solution, the H+ and Cl- ions dissociate completely; but the NH4+ ions in solution bind with some of the OH- ions in the water to form NH4OH. This leaves an excess of H+ ions in the water, making it slightly acidic.
c is a base, and a and b are solids.
a, b, and c are all solids and c is the base
The first two answers above are completely wrong. A is the only solid among all the choices. All sulfates are soluble except for the sulfates containing, Ag, Pb, Hg, Ca, Sr, or Ba. Answers B, C, and F are all soluble in water and aren't solids. D and E are water so they can't be classified. The acids are D,E, and F. The bases are D and E. D and E are both an acid and base because water is an amphoteric substance (it can act as either a base or acid depending on what it is reacted with).
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: