According to the following equation, (1kcal = 1000cal &1 cal=4.18J) (A) How much heat is needed to decompose 40 grams of CaCO3? (B) What mass of CaCO3 can be decomposed by 100 kcal? (C) At STP (22.4L=1mol) how many mL of gas can be produced from 845KJ of energy? CaCO3 ---> CaO + Co2 Delta H= 176KJ/mol
A) first convert the 40 g of CaCO3 to moles. 40 grams CaCO3 x (1 mol/100.09 g) = 0.3996 mol CaCO3 Then using the information from the equation, convert moles to kJ 0.3996 mol CaCO3 x (176 kJ/1 mol)= 70.3 kJ So 70.3 kJ are needed. B) Convert the 100kcal to cal 100 kcal=100,000 cal Convert cal to J 100,000 cal=418,000 J Convert J to kJ 418,000 J=418 kJ Using the info from the equation, convert kJ to mol 418 kJ x (1 mol/176 kJ)= 2.375 mol Convert moles to grams 2.375 mol x (100.09 g/mol)=237.7 g So 237.7 grams can be decomposed C) convert kJ to mol from the info in the equation 845 kJ x (1 mol/176 kJ)=4.8 mol Convert mol to L with the equation 4.8 mol x (22.4 L/1 mol)=107.5 L Convert L to mL 107.5 L=107,500 mL So it can occupy 107,500 mL.