Answer to Question #149845 in General Chemistry for taiya

Question

What mass of O2 is needed to increase the temperature of 35 grams polyethylene from 250K to 375. K? (specific heat of polyethylene is 0.551 cal/gK)
P4 + 5O2 --> P4O10 ∆H = - 3013 kJ/mol

Answer 1

First calculate the amount of heat needed to increase the temperature of 35 grams of polyethylene from 250K to 375K:

$Q = cm\Delta T = 0.551 * 35 * (375-250) = 2410.6 (cal)$

Convert calories to joules (1 cal = 4.184 J):

$Q = 2410.6 * 4.184 = 10086 (J) = 10.09 (kJ)$

Find the mass of O₂ needed to produce 3013 kJ of heat (5 moles according to the equation):

$m(O_2) = M*\nu = 32 * 5 = 160 (g)$

If 160 g of O₂ are needed to produce 3013 kJ of heat, then calculate the amount of NO₂ needed to produce 10.09 kJ of heat:

$m(O_2) = 160 * 10.09/3013 = 0.536 (g)$

Answer: 0.536 g of O₂ is needed to increase the temperature of 35 grams of polyethylene from 250K to 375K.