CHEM 1A

Can someone please help me.....
I have limited reactant formula problem. I am completely lost.

2Ca(s) + O2(g) ----> 2CaO(s)

Calculate the mass of Calcium Oxide that can be prepared from 6.87g of Ca and 4.58g of O2.

I calculated 2Ca to .171mol and O2 to .286mol, I am lost from here...

  1. 👍 0
  2. 👎 0
  3. 👁 229
asked by Chad
  1. This is a limiting reagent (LR) problem and I work these the long way and probably not at all like your prof does. But here goes.

    mols Ca = 6.87/atomic mass Ca = approx 0.171 which you have.
    mols O2 = 4.58/32 = approx 0.143 ( you used the atomic mass of O and not the molar mass of O2).

    The next step is to convert mols Ca to mols CaO AND convert mols O2 to mols CaO.
    First Ca to CaO is 0.171 x (2 mol CaO/2 mol CaO) = 0.171 mols CaO formed IF we had all of the O2 we needed.
    Next O2 to CaO is 0.143 x (2 mols CaO/1 mol O2) = 0.286 mols CaO IF we had all of the Ca we needed.
    These two values are the same so one of them must be wrong. The correct value in LR problems is ALWAYS the smaller value so the correct value is we form 0.171 mols CaO and Ca is the limiting reagent.
    Now use the smaller value and grams CaO = mols x molar mass.

    1. 👍 0
    2. 👎 0
    posted by DrBob222
  2. Sweet. Thank you. I was real close. I was just calc ing the moles wrong at the end.
    Thanks again

    1. 👍 0
    2. 👎 0
    posted by Chad

Respond to this Question

First Name

Your Response

Similar Questions

  1. Chemistry Help

    I have tried usingg the molecular formula, formulas in the text book but my answers dosent match any of the multiple choice answers, can someone help? For each of the reactions shown, calculate the mass (in grams) of the product

    asked by Kelly on October 5, 2010
  2. Chemistry PLEASE HELP:(

    I really need someone to explain this stoichiometry problem. Directions: Outline how to determine the limiting agent. Determine the excess reactant and how much is left over. Determine the amount of each of the products produced.

    asked by Shelbie on January 11, 2013
  3. Chemistry

    Hello! I'm doing these questions for my chemistry homework, and I can only figure out the first one, I don't know how to do the rest, I'm completely stuck! Please help!! Thank you! 1.) For the reaction, calculate how many grams of

    asked by J.J on March 18, 2014
  4. chem

    what are the type of chemical reactions for the below (synthesis, double/single displacement or decomposition) 2Na+2H2O->2NaOH+H2 2FeS2+3O2->Fe2O2+2SO2 CaCO3->CO2+CaO 2H2S+2KOH->K2S+2HOH 2Ca+4HOH->2Ca(OH)2+H2

    asked by Sam on March 12, 2014
  5. chemistry

    For each of the following precipitation reactions, calculate how many grams of the first reactant are necessary to completely react with 17.5 of the second reactant.

    asked by Aaron on April 27, 2012
  6. chemistry

    Calculate how many grams of the first reactant are necessary to completely react with 55.8g of the second reactant. Na2CO3 + CuCl2 → CuCO3 + 2 NaCl

    asked by Cristin on September 25, 2014
  7. Chemistry

    When 28g calcium reacts with 25 grams oxygen, how many grams calcium oxide form? I have 2Ca+ 2O2= 4CaO its is not working. Stoichemistry. I have the Ca as the reactant that is limiting? Please help.

    asked by Sarah on March 20, 2016
  8. Chemistry

    For each of the following precipitation reactions calculate how many grams of the first reactant are necessary to completely react with 55.8 g of the second reactant. K2SO4 + Sr(NO3)2 + SrSO4 + 2KNO3

    asked by Harold on January 25, 2017
  9. Chemistry

    For each of the following unbalanced equations, suppose that exactly 15.0g of each reactant is taken. Determine which reactant is limiting, and calculate what mass of each product is expected. assume the limiting reactant is

    asked by Megan on February 16, 2009
  10. chem

    can you explain? For each of the reactions shown, calculate how many grams of the product form when 16.8 g of the reactant in bold completely reacts. Assume that there is more than enough of the other reactant. 4 Cr(s) + 3 O2(g) 2

    asked by hannah on December 6, 2010

More Similar Questions