chemistry 1

posted by .

if 20.2g of zn react with and equal amount of magnesium chloride to form magnesium and zinc chloride[zn+mgcl2>
a.what is the limiting reactant?
b. how much magnesium will be produced?

Here is the way to solve most of these stoichiometry problems.
Step 1. Write the balanced equation.
Zn + MgCl2 ==> Mg + ZnCl2

Step 2. Convert what you have into mols.
2a. mols Zn = 20.2/65.4 = 0.309
2b. mols MgCl2 = 20.2/95.2 = 0.212

Step 3. Using the coefficients in the balanced equation, convert each of the mols from what you have (in this case mols Zn and mols MgCl2) to mols of what you want (in this case Mg is the product).
3a. First from 2a (mols Zn).
mols Mg = mols Zn x (1 mol Mg/1 mol Zn) = 0.309 x 1/1 = 0.309 mols Mg product.

3b. from 2b (mols MgCl2).
mols Mg = mols MgCl2 x (1 mol Mg/1 mol MgCl2) = 0.212 x 1/1 = 0.212.

3c. Now you make a decision. Both answers can't be correct; i.e., 3a says 0.309 mol Mg will be produced while 3b says 0.212 mols Mg will be produced. The answer ALWAYS is the smaller one AND MgCl2, then, is the limiting reagent. (That answers part a of the problem.)

Step 4. The problem doesn't state if you want mols, grams, or what. If you want mols, then 0.212 mol Mg will be produced. If you want grams, then
mols Mg x atomic mass Mg = grams Mg.

If you haven't seen this method before, it might be good to learn it. It will work literally hundreds of problems for you. If you don't have a limiting reagent problem, and many are not, simply omit steps 2b, 3b, and 3c.

You need to go through and correct any numbers for atomic masses of Zn, Mg, and molar mass MgCl2 for I estimated those values. They are close but may not be the best. Look them up on the periodic table.

Finally, I want you to know that this reaction will not take place but the reverse one will. That is, Mg will displace Zn from ZnCl2 in this reaction
Mg + ZnCl2 ==> Zn + MgCl2 but the reaction will not take place as it is writtenin the problem. Technically, then, the answer to the problem is that NO Mg will be produced; however, I don't think that is the intent of the problem. The steps I showed are the actual steps you will need for a valid reaction and they work equally well for reactions that will not occur.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry - Stoichiometry

    16.2g of magnesium reacts exactly with 25.3g of fluorine to produce magnesium fluoride, the only product. How many grams of magnesium fluoride could be produced from the reaction of 10.5g of magnesium with excess fluorine. This is …
  2. AP Chemistry

    When hydrochloric acid reacts with magnesium metal, hydrogen gas and aqueous magnesium chloride are produced. What volume of 5.0 M HCI is required to react completely with 3.00 g of magnesium?
  3. chemistry

    7. Write the balanced equation for the equation for the reaction of magnesium with HCl. What is the mole ratio between magnesium and magnesium chloride will be produced?
  4. chemistry

    Suppose 50.0 grams of magnesium reacts with 71.0 grams of hydrochlorie acid according to the foloowing equation: Mg(s) + 2HCl(aq) -> MgCl2(s) + H2(g) 1) What is the maximum mass of magesium chloride that can be produced?
  5. Chemistry

    When hydrochloric acid reacts with magnesium metal, hydrogen gas and aqueous magnesium chloride are produced. What volume of 9.0 M HCl is required to react completely with 5.00 g of magnesium?
  6. chemistry hw question

    Magnesium hydroxide + hydrogen chloride-----> magnesium chloride + water How many grams of magnesium chloride can be produced from 14.60 mL of a 0.546M hydrogen chloride solution?
  7. Chemistry

    A solution of magnesium chloride, MgCl2, is prepared by dissolving 19.0g of MgCl2 in 250 mL OF water. a.) Calculate the weight percent of magnesium chloride in solution. b.)The denstiy of the above solution is 1.05 g/mL. Calculate …
  8. Chemistry 1300

    1) Aluminum metal reacts with chlorine gas to form solid aluminum trichloride, AlCl3. What mass of chlorine gas (Cl2) is needed to react completely with 163 g of aluminum?
  9. chemistry

    When hydrochloric acid reacts with magnesium metal, hydrogen gas and aqueous magnesium chloride are produced. What volume of 4.8 M is required to react completely with 2.60 g of magnesium?
  10. Chemistry

    4.13 grams of magnesium chloride were recovered after the chemical reaction between magnesium and chlorine gas occurred. If 7.10 grams of magnesium chloride was suppose to be produced, what is the percent yield of magnesium chloride?

More Similar Questions