Question

Try to solve these problems using the Table method

3. Combustion analysis was performed on 1.50 g of a compound containing C, H and N to yield 3.21 g of carbon dioxide and 0.981 g of water. What is the empirical formula of this compound?

4. A 3.82-g sample of magnesium nitride is reacted with 7.73 g of water. Mg3N2 (s) + 3 H2O (ℓ) → 2 NH3 (g) + 3 MgO (s) The yield of MgO is 3.60 g. What is the percent yield in the reaction?

5. a) A beaker contains 200.0 mL of 0.250 M AgNO3. 200 mL of 0.100 M HCl(aq) is added to it. What is the NO3 − concentration in the final mixture?

b) What is the Ag+ concentration in the final mixture?

Please explain why

Answer 1

Q3) The mass of CO2(3.21g) given is wrong, as it isgiving 183% of CO2 . So can't give this answer.

4) In this reaction magnesium nitride is the limiting reagent and the product is calclated from it.

one mole of nitride gives 3 moles of oxide

100g of nitride gives 3x 40 g of oxide

3.82 g gives = 3.82 x3x 40/100 = 4.584 g

Thus the theoretical yield of magnesium oxide is 4.584 g

isolated yield = 3.6g

Thus percentage yield = 3.6x100/4.584 = 78.53 %

5)    AgNO3       + HCl             -------> AgCl(s)      + HNO3

         200x0.25            200x0.10                     0                  0 initial cconcentrations

     = 50                       =20

   [Ag+] = 50/400 = 0.125M and [Cl-] = 20/400 =0.05M initially

Now the ionic product of [ag+][Cl-] = 0.125x0.05 is more than its Ksp and all silver is precipitated as silver chloride.

All nitrate is present in solution = 0.125M

b) the [Ag+] = square root of its Ksp as all the silver is precipitated as AgCL and the only aconcentration of Ag+ that can be in solution in equilibrium with solid is its solubility. that is square root of its Ksp.

approximatelys 1.0x 10^-5M