Question

To prevent waste, a chemistry department converted a lab procedure to a microscale version. The total quantity of 1 M HCl used by one pair of students for each procedure is given in the table. There are 156 students in the course. Large scale quantity 97.1 mL Microscale quantity 14.6 mL Given that 1500 kW.hr (kilowatt-hours) of electricity are required to produce 1 Mg (megagram) of HCl, calculate the amount of energy saved by converting the procedure to a microscale version. Note: 1 kW.hr = 3.6 MJ (megajoules) The energy saved is equivalent to using a 60 W light bulb energy saved = for about hours.

Answer 1

Volume of HCl solution saved = 97.1 - 14.6 = 82.5 mL

Moles of HCl = Volume * Molarity = 82.5 * 10^-3 * 1.00 = 0.0825 moles

Mass of HCl = molar mass * moles = 36.5 * 0.0825 = 3.011 g

Energy saved = mass of HCl * 1500 / 1 Mg HCl = 3.011 * 1500 / (10⁶ g) = 4.52 * 10^-3 Kilo watt hr = 4.52 * 10^-3 * 3.6 * 10³ KJ

= 16.27 KJ

Energy saved by 78 pairs = 16.27 * 78 = 1269.06 KJ