Question

Solid phosphorous is found in two forms: white phosphorous (P4) and red phosphorous (P). White phosphorous is the standard state. The enthalpy of the formation of red phosphorus is -17.6kJ.

When 32.6 g of white phosphorous reacts to form red phosphorous. What is the enthalpy change?

Answer 1

Note the correct spelling of phosphorus. The word you spelled is a word but not the correct one for the element, either P4 or P. For example, H3PO3 is phosphorous acid.

P4 ==> 4P + 17.6 kJ.

17.6 kJ x (32.6/3*molar mass P4) = ? and it is exothermic which makes the sign for delta H negative.