Try to solve these problems using the Table method 3. Combustion analysis was pe
ID: 917485 • Letter: T
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 () 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
Explanation / Answer
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
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