Question

Calculate the heat required to sublime 20.0 grams of dry ice (solid carbon dioxide) at a temperature of -78.5 °C, given the heat of sublimation of CO2 is 25.2 kJ/mol.

Answer 1

First, we need to determine the number of moles of CO2 in 20.0 grams of dry ice. The molar mass of CO2 is 12.01 g/mol  for carbon  + 2 * 16.00 g/mol  for oxygen  = 44.01 g/mol.Number of moles =  mass of CO2  /  molar mass of CO2 Number of moles = 20.0 g / 44.01 g/mol = 0.4545 molNow, we can calculate the heat required to sublime the dry ice using the heat of sublimation.Heat required =  number of moles  *  heat of sublimation Heat required = 0.4545 mol * 25.2 kJ/mol = 11.45 kJTherefore, the heat required to sublime 20.0 grams of dry ice at -78.5 C is 11.45 kJ.