<li><p>What is the minimum number of moles of
PbSO4 that must be used to prepare 1 liter of
saturated PbSO4 solution at 25°C? (Ksp at
25°C for PbSO4 =1×10−8 )
(A) 1×10−16mol
(B) 1×10−8mol
(C) 1×10−4mol
(D) 1×10−2mol
(E) 1×10−1mol</p></li>
<li><p>Zinc metal will
reduce Cu2+ in
solution
BECAUSE zinc is a more active
metal than copper is.</p></li>
</ol>
<p>How do you answer these?</p>
<ol>
<li><p>T, T, CE. Zinc degrades spontaneously to Za2+ and 2e- while copper tends to take up electrons and form molecules, its just something you need to know. Copper, Silver, Gold, Zinc, Mercury, etc, tend to form molecules and Potassium, Sodium, etc, give off electrons. Look up reactivity series on wikipedia.</p></li>
<li><p>I think it's C because 1x10-8 = [Pb2+][SO42-], so 1 mole of PbSo4 would be the sqrt of 1x10-8 which is 1x10-4. Not exactly sure though</p></li>
</ol>