Chemistry

posted by .

Mg(s) + 2 HCl(aq) --> MgCl2(aq) + H2 (g) DeltaH= -4.6x10^2 kJ

How much heat is evolved when 0.598 g of Mg are dissolved in excess HCl?

I'm not sure how to go about this problem. What I thought to do was:

0.598 g x 1 mol Mg/24.31 g Mg x 2 mol HCl/ 1 mol Mg x 36.46 g HCl/ 1 mol HCl = 1.79 g HCl
and from here I am not sure what to do. Somehow I need to incorporate the DeltaH into a formula, I believe.

  • Chemistry -

    Your approach is to perform a stoichiometry calculation to find the grams HCl but that isn't what the problem is asking. Try something like this.
    You know dissolving 1 mole Mg (24.3 g) in HCl produces 4.6E2 kJ. So how much heat will just 0.598 g Mg evolve?
    That will be
    4.6E2 kJ x 0.598/24.3 = ??

  • Chemistry -

    So the grams must cancel each other out when we divide and it leaves us with just kJ? So -11.3 kJ

  • Chemistry -

    Yes, but I notice there are only two significant figures in 4.6E2; therefore, the answer should not contain more than two. I would round 11.3 kJ to 11 kJ energy released (-11 kJ for delta H).

  • Chemistry -

    Oh that's right, thank you!

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Honors Chemistry

    On the same subject as before with the limiting/excess reagent stuff -- can someone please check my answer to make sure I'm doing it right?
  2. Chemistry

    Hi, Please provide assistance on the following problem. I worked out part of it, but do not know what to do after calculating pH for HCl. Suppose you dissolved 0.0365 grams of HCl in water to give a final volume of 10.0 mL. The molar …
  3. Chemistry

    If 1.22 grams of magnesium reacts with 100 ml of 6.02 M HCl solution. How much heat is evolved?
  4. chemistry

    Consider the following reaction: 2H2 (g) + O2 (g)  2H2O (l) ΔH = -572 kJ a. How much heat is evolved for the production of 1.00 mol H2O (l)?
  5. Chemistry

    If Chelcy and Allyson reacted 2.55 grams of Mg with excess hydrochloric acid (HCl), how many grams of MgCl2 will they theoretically produce?
  6. Chemistry

    A sample of impure magnesium was analyzed by allowing it to react with excess HCl solution: Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g) After 1.27 g of the impure metal was treated with 0.100 L of 0.768 M HCl, 0.0125 mol HCl remained. …
  7. Chemistry

    How much heat is evolved when 500kg of Ammonia is evolved according to the following equation: N2(g)+3H2(g)<->2NH3(g) [deltaH =-91.8K]
  8. chemistry

    Mg+2Hcl---mgcl2+h2 volume of h2=40ml Hcl is 6M what mass os h is obtained by addin excess hcl to 6m of magnesium
  9. chemistry

    Consider these reactions where M represents a generic metal 1. 2M(s) +6HCl(aq) --> 2MCl3(aq)+3H2(g) (deltaH)= -725.0 kj 2. HCl(g)-->HCl(aq) (deltaH)= -74.8kj 3. H2(g)+CL2(g) --> 2HCl(g) (deltaH)=-1845.0kj 4. MCL3(s) --> …
  10. Chemistry

    Magnesium metal reacts with HCl(aq) according to the equation: Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g) In an experiment to determine the ΔH for this reaction, 0.158 g of Mg metal is combined with an excess of HCl to make 100.0 mL …

More Similar Questions