General Chemistry

Isotopic abundance Calculation and Limiting reactions worksheet:

1. Naturally occurring magnesium has three isotopes with 12,13,14 and neutrons. Determine the mass numbers and write the symbols of these three isotopes.

2. Hydrazine is composed of 87.42% nitrogen and 12.58% hydrogen by mass. Its experimentally determined molar mass is 32.05 g/mol. Determine the empirical and molecular formulas of hydrazine.

Ans: Empirical Formula: NH3; Molecular Formula: N2H6.

3. A 63.47 g sample of an ionic compound contains 17.17 g sodium and 10.46 g nitrogen; the rest is oxygen. The compound’s molar mass is 84.99 g/mol. Determine its formula.  Ans: NaNO3.

Here Mass of Oxygen is not given. Thus, we can find as below and other process is simple as we did in other problems.

 

4. Write the balanced equation for the reaction that occurs when 23 grams of iron (II) chloride is mixed with 41 grams of sodium phosphate forming iron (II) phosphate and sodium chloride. If 16.1grams of sodium chloride are formed in the reaction, what is the percent yield of this reaction?

FeCl2  +  Na3PO4  →

5. Silver nitrate, AgNO3, reacts with ferric chloride, FeCl3, to give silver chloride, AgCl, and ferric nitrate, Fe(NO3)3.  In a particular experiment, it was plannned to mix a solution containing 25.0 g of AgNO3 with another solution containing 45.0 grams of FeCl3.

a.

a) Write the chemical equation for the reaction.

b) Which reactant is the limiting reactant?

c)  What is the maximum number of moles of AgCl that could be obtained from this mixture?

d)  What is the maximum number of grams of AgCl that could be obtained?

e)  How many grams of the reactant in excess will remain after the reaction is over?