The water gets cold because the ice cube is endothermic. Which means it takes in heat. It takes the warmth from the water and melts the ice cube which the ice cube releases coldness which cools down the water.
The mole ratio of PbO2 to water in
Pb + PbO2 +2 H2SO4 = 2PbSO4 + 2H2O is
1 :2
1 mole of Pb reacted with 1 mole of PbO2 and 2 moles of H2SO4 to form 2 moles of PbSO4 and 2 moles of H2O
therefore the mole ratio of Pbo2 to H2O is 1:2
The reaction is a single replacement reaction, as the aluminum is REPLACING the copper attached to the sulfate. the exponents on the equation, in order, would be 2, 3, 1, 3. The reaction represents a chemical change because a new compound is being formed; if the original compound was simply changing state ( from liquid to gas, etc), then the change would be physical.
The last question requires some stoichiometry. My work is attached.
D. Sonic booms. Hope this helps
The inventor of the cotton gin in Eli Whitney