$7\mathrm{.}50.$Eight fluid ounces $(1$qt$=32$oz$)$of a beverage in a glass at $18\mathrm{.}0$C $$is to be cooled by adding ice and stirring. The properties of the beverage may be taken to be those of liquid water. The enthalpy of the ice relative to liquid water at the triple point is $-348$kJkg$.$Estimate the mass of ice $($g$)$that must melt to bring the liquid temperature to $4$C$,$neglecting energy losses to the surroundings. $($Note: For this isobaric batch process, the energy balance reduces to Q$=$H$).$

a$.$If the pump is $70\%$efficient $($i$.$e$.,30\%$of the electrical energy delivered to the pump is not used in pumping the water$),$what is the required pump horsepower?

b$.$Even if we assume that the iron oxide binds $100\%$of the arsenic, what other factors limit the effectiveness of this operation?