Chemistry

posted by .

Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g) delta H1?

MgO(s) + 2HCl(aq) ->MgCl2(aq) + H2O(l) delta H2?

To make these equations add up to the formation reaction of MgO, you will need to include the following:

H2(g) + 1/2O2(l) delta H =-241.8 kJ

Using Hess's Law and manipulating these three equations and their respective enthalpy values you can solve for deltaH formation of MgO.

The equations above are already balanced so so I do not understand what they mean by manipulating the equations. To find the delta H value for the first two is this when I use the sum of products - the sum of reactants?

  • Chemistry -

    The only problem is that when I looked up the thermodynamic values I could not find MgCl2(aq) so would this just be 0?

  • Chemistry -

    For the first equation I did
    0 + 2(-167.159) -> 0 + 0
    0 - 334.318 = deltaH1 = -334.318

    Second equation I did
    -601.24 + (-334.318) -> -285.83
    -285.83 -(-935.558) = deltaH2 = 649.728

    Then deltaH3 = -241.8

    On my lab report it says to find the deltaH formation of MgO and it has two columns, one for Mg and MgO. So is deltaH1 my Mg and deltaH2 my MgO?

  • Chemistry -

    I will refer to the three equations you have above as eqn 1, eqn 2 and eqn 3.
    Write equn 1 as is/
    Reverse eqn 2.
    Eqn 3 as is
    Add the three equations together and you see that you get
    Mg(s) + 1/2 O2(g) ==> MgO(s)
    The delta H1 for eqn 1 is the delta H you measured.
    Delta H2 for eqn 2 is the delta H you measured but since you reversed the equation you want to change the sign. Eqn 3 has dH given.
    Add those 3 as I've shown and you obtain the dH formation for MgO.

  • Chemistry -

    you are correct

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    In the classroom, we reacted Mg(s) + 2HCl -> MgCl2(aq) + H2 (g) (0.31 g of Mg(s), and 99.46 g of HCl) Initial temp. = 22.5 celsius, max. temp. 36.0 celsius and MgO(s) + 2HCl -> MgCl2(aq) + H2(g) (1.00 g of MgO(s) and 97.71 g …
  2. chemistry

    1) MgO (s) + 2H (aq) -> Mg+2 (aq) + H2O (l) 2) Mg+2 (aq) + H2 (g)-> Mg(s) + 2H+ (l) 3) equation 1+ equation 2 = MgO (s) + H2 (g) -> Mg (s) + H2O (l) is it correct?
  3. Chemistry

    Mg + 2HCl -> MgCl2 +H2 delta H = ? MgO + 2HCl (aq) -> MgCl2+ H2O delta H = ?
  4. chemistry

    My chem book gives me the following Hess' Law example: Mg + 2HCl --> H2 MgCl2 Delta H1 MgO +2HCl --> H2O +MgCl2 Delta H2 H2 + 1/2 O2 --> H2O Delta H3=-68.3kcal The desired reaction is the formation reaction of MgO as follows: …
  5. Chemisty

    Calculate the standard enthalpy change for the following reaction at 25 °C. MgCl2(s)+H2O(l)-->MgO(s)+2HCl
  6. Chemistry

    Calculate the standard enthalpy change for the following reaction at 25 °C. MgCl2(s) + H2o(l) ---> MgO(s) + 2HCl(g)
  7. Chemistry

    Calculate the enthalpy change of formation for the following reactions using Hess's law, and the enthalpies of formation given in Figure 4: b) MgO +2HCl --> MgCl2 +H2O c)NaOH+ HCl -->NaCl +H20 Figure4: the given enthalpies of …
  8. Chemistry

    The combustion reaction of Mg +1/2 O2-->MgO produces a very bright white flame and high heat. Verify that the following reactions produce the same overall reaction: a) MgO+2HCl-->MgCl2+H2O b) Mg+2HCl-->MgCl2+H2 c) H2+1/2O2-->H2O …
  9. Chemistry

    A 1.0-g sample of MgCl2 produced a 10.00C increase in a calorimeter charged with 40.0mL of deionized water. The specific heat is of MgCl2 is 0.750J/C*g. What is the value of delta(s)H for MgCl2?
  10. Chemistry

    A 1.0-g sample of MgCl2 produced a 10.00C increase in a calorimeter charged with 40.0mL of deionized water. The specific heat is of MgCl2 is 0.750J/C*g. What is the value of delta(s)H for MgCl2?

More Similar Questions