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# Redox, Oxidation Numbers, Limiting Reagent, Yield Problems

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1. One of the steps in the commercial process of converting ammonia to nitric acid is the conversion of NH3 into NO:
4NH3(g) + 5O2(g) ---> 4NO(g) + 6H2O(g)

In a certain experiment, 2.25 g of NH3 reacts with 3.75 g of O2.
a) Which is the limiting reactant?
b) How many grams of NO form?
c) How many grams of the excess reactant remain after the limiting reactant is completely consumed?

2. Tartaric acid, H2C4H4O6, has two acidic hydrogens (this acid is often present in wines and precipitates from solution as the wine ages). A solution containing an unknown concentration of the acid is titrated with NaOH. It requires 22.62 mL of 0.2000M NaOH solution to titrate both acidic protons in 40.00 mL of tartaric acid solution. Write a balanced net ionic equation for the neutralization reaction and calculate the molarity of the tartaric acid solution.

3. Glycerol, C3H8O3, is a substance used extensively in the manufacture of cosmetics, foodstuffs, antifreeze, and plastics. Glycerol is a water-soluble liquid with a density of 1.2656 g/mL at 15oC. Calculate the molarity of a solution of glycerol made by dissolving 50.000 mL of glycerol at 15oC in enough water to make 250.00 mL of solution.

4. A solution is made by mixing 50.0 mL of 6.00 M HCl, 100.0 mL of 1.00 M HCl, and enough water to make 250.0 mL of solution. What is the molarity of HCl in the final solution?

5. Balance each of the following redox reactions

a) Cr2O72-(aq) + CH3OH(aq) ----> HCO2H(aq) + Cr3+(aq) (Acidic Sol'n)
b) H2O2(aq) + ClO2(aq) ----> ClO2-(aq) + O2(g) (Basic Sol'n)

6. Determine the oxidation number for the indicated element in each of the following compounds:
a. Ti in TiO2
b. Sn in SnCl3-
c. C in C2O42-
d. N in N2H4
e. N in HNO2
f. Cr in Cr2O72-

© BrainMass Inc. brainmass.com October 24, 2018, 10:06 pm ad1c9bdddf
https://brainmass.com/chemistry/oxidation-reduction-and-electrochemistry/redox-oxidation-numbers-limiting-reagent-yield-problems-148237

#### Solution Summary

A great amount of detail is included in the solution of many redox, oxidation numbers, limiting reagent and yield problems.

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## Assorted General Chemistry Problems

1.28) a. A cube of osmium metal 1.500cm on a side has a mass of 76.31g at 25°C. What is the density in g/cm3 at this temperature? b. The density of titanium metal is 4.51g/cm3 at 25°C. What mass of titanium displaces 65.8mL of water at 25°C? c. The density of benzene at 15°C is 0.8787g/mL. Calculate the mass of 0.1500L of benzene at this temperature.

1.70) Automobile batteries contain sulfuric acid, which is commonly referred to as "battery acid." Calculate the number of grams of sulfuric acid in 0.500L of battery acid if the solution has a density of 1.28g/mL and is 38.1% sulfuric acid by mass.

2.10) In a series of experiments, a chemist prepared three different compounds that contain only iodine and fluorine and determined the mass of each element in each compound:
Compound Mass of Iodine (g) Mass of fluorine (g)
1 4.75 3.56
2 7.64 3.43
3 9.41 9.86
a. Calculate the mass of fluorine per gram of iodine in each compound. b. How do the numbers in the first part of the question support the atomic theory?

2.30) The element lead (Pb) consists of 4 naturally occurring isotopes with atomic masses 203.97302, 205.97444, 206.97587, and 207.97633amu. The relative abundances of these 4 isotopes are 1.4, 24.1, 22.1, and 52.4%, respectively. From these data, calculate the atomic weight of lead.

2.48) Fill in the gaps in the following table:
Symbol 75As^3-
Protons 28 53
Neutrons 31 74 118
Electrons 26 76
Net charge 1- 3+

3.52) a. The characteristic odor of pineapple is due to ethyl butyrate, a compound containing carbon, hydrogen, and oxygen. Combustion of 2.78mg of ethyl butyrate produces 6.32 mg of CO2 and 2.58mg of H2O. What is the empirical formula of the compound? b. Nicotine, a component of tobacco, is composed of C,H, and N. A 5.250-mg sample of nicotine was combusted, producing 14.242mg of CO2 and 4.083mg of H2O. What is the empirical formula for nicotine? If the substance has a molar mass of 60+-5g/mol, what is its molecular formula?

3.100) Aspirin (C9H8O4) is produced from salicylic acid (C7H6O3) and acetic anhydride (C4H6O3):
C7H6O3+ C4H6O3&#61664; C9H8O4+HC2H3O2
a. How much salicylic acid is required to produce 1.5X10^2kg of aspirin, assuming that all of the salicylic acid is converted to aspirin? b. How much salicylic acid would be required if only 80% of the salicylic acid is converted to aspirin? c. What is the theoretical yield of aspirin if 185kg of salicylic acid is allowed to react with 125kg of acetic anhydride? d. If the situation described in part c. produces 182kg of aspirin, what is the percentage yield?

4.52) Which of the following are redox reactions? For those that are, indicate which element is oxidized and what is reduced. For those that are not, indicate whether they are precipitation or acid-based reactions.
a. Cu (OH) 2(s) + 2 HNO3 (aq) &#61664; Cu (NO3)2(aq) + 2 H2O (l)
b. Fe2O3(s) + 3 CO (g) &#61664; 2 Fe(s) + 3 CO2 (g)
c. Sr (NO3)2(aq) + H2SO4 (aq) &#61664; SrSO4(s) + 2 HNO3 (aq)
d. 4 Zn(s) + 10H+ (aq) +2 NO3-(aq) &#61664; 4 Zn2+ (aq) + N2O (g) + 5 H2O (l)

4.102) Tartaric acid, H2C4H4O6, has two acidic hydrogens. The acid is often present in wines and precipitates from solution such as the wine ages. A solution containing an unknown concentration of the acid is titrated with NaOH. It requires 22.62 mL of 0.2000M NaOH solution to titrate both acidic protons in 40.00 mL of the tartaric acid solution. Write a balanced net ionic equation for the neutralization reaction, and calculate the molarity of the tartaric acid solution.

4.111) A mixture contains 76.5% NaCl, 6.5% MgCl2, and 17.0% Na2SO4 by mass. What is the molarity of Cl- ions in a solution formed by dissolving 7.50 g of the mixture in enough water to form 500.0 mL of solution?

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