1. S

    The Story Behind Hess Law

    My book introduces Thermochemistry with the concept of heat and how a calorimeter works. After that, it explains the story behind Hess Law and says that one of the reasons it was created is because a calorimeter can't calculate fast chemical reactions, but it doesn't really say the problem with...
  2. S

    Enthalpy & Hess's Law

    Hello everyone, I need quite urgent help. I have carried out experimentally two reactions as follows: 1. CaO + H2O -> Ca(OH)2 2. Ca(OH)2 + 2HNO3 -> Ca(NO3)2 + 2H2O to prove Hess's Law for this reaction: 3. CaO + 2HNO3 -> Ca(NO3)2 + H2O How do I do calculate the enthalpies? Is q=mcΔT enough...
  3. S

    Hess' Law problem

    Given : ClO(g) + O3(g) ---> Cl(g) + 2 O2(g) delta H of rxn= -29.90kJ 2 O3(g) ----> 3 O2(g) delta H of rxn= 24.18kJ Determine the value of heat of reaction for the following: Cl(g) + O3(g) ----> ClO(g)+O2(g) Delta H = ? ============================================================...
  4. B

    Hess's Law

    Can somebody please explain how to do the following two questions, please? 1.For the reaction 4Fe(s) + 3O2(g) --> 2Fe2O3(s) how much heat would be liberated by the combustion of 5.00 g of iron metal in excess oxygen? 2. If 3.00 g iron metal are reacted in a calorimeter with a heat capacity of...
  5. T

    LR Meets Hess's Law

    Fe2O3 + 6HCl → 2FeCl3 + 3H2O How much heat is produced when 2.6 g of Fe2O3 react with 0.91g of HCl? For some reason, my brain is broken and I cannot remember how to even start this problem. Chemistry evades me completely this afternoon. I just need the steps to complete.
  6. S

    Hess's Law

    I am given the enthalpies of combustion C=-393.5, H2=-285.8, C2H5OH=-1366.7 I need to find the standard enthalpy change (deltaH) of the reaction; 2C+2H2+H20(l)->C2H5(OH) I keep getting 293.9, but i'm not sure if this is correct.
  7. T

    Hess law problem

    I can't find the answer , Can anybody help? A+2B--->2C (-100kj) 1/5A--->D+2C (-200kj) B+2D--->A (+50kj) A+B--->2C (?kj) 1)-150 2)+450 3)+150 4)-450 The answer is -150 kj but I need a step by step explanation.... Thanks
  8. C

    Hess' Law and Heat of Formation of MgSo4

    I have never taken anything like this before and I am very confused on how to even begin. Using the loggerpro and the calorimeter I need to determine the heat of formation for Mg and MgSO4. Here are the equations for Mg: Initial y=-0.0001321x+20.3 Final y=-0.0007852x+30.69 I know the mass of...
  9. G

    Hess's Law

    The original equation is: 4Fe+3O2-->2Fe2O3 H=-1652KJ My equations are: 1) Fe+3H2O-->fe(OH3)+3/2(H2) h=160.9KJ 2) H2+1/2(O2)-->H2O H=-285.8KJ 3) Fe(OH3)-->Fe2O3+3H2O H=288.6KJ Using Hess's law how do I get this back to the original equation?