Need a little help to check my work on these exercises. Answers to a few of them
ID: 852806 • Letter: N
Question
Need a little help to check my work on these exercises. Answers to a few of them would be very helpful. I also posted my answers next to each question.
1.) A student titrating a sample of a powdered aspirin tablet to find out how much acetylsalicylic acid is in the sample finds that it requires 29.38 mL of a 0.093M sodium hydroxide solution to neutralize the acid in the sample. How many milligrams of acetylsalicylic acid did the sample contain? My Answer: 493.3 mg
2.) Students working in lab accidentally spilled 2.8 L of 3.0 M H2SO4 solution. They find a large container of acid neutralizer that contains baking soda, NaHCO3. How many grams of baking soda will be needed to neutralize the sulfuric acid spill? My Answer: 1411.3 g
3.) A powder contains benzoic acid mixed with starch. A student finds that a 4 g sample of this powder requires 35.01 mL of a 0.095M sodium hydroxide solution for the acid to be neutralized. What is the percent by mass of benzoic acid in the powder? My Answer: 10.15%
4.) Barium oxalate is used as a colorant to produce the green color in fireworks. Imagine that you have been assigned to prepare barium oxalate by reacting barium hydroxide octahydrate (Ba(OH)2
Explanation / Answer
1.) A student titrating a sample of a powdered aspirin tablet to find out how much acetylsalicylic acid is in the sample finds that it requires 29.38 mL of a 0.093M sodium hydroxide solution to neutralize the acid in the sample. How many milligrams of acetylsalicylic acid did the sample contain? My Answer: 493.3 mg
Moles of NaOH=0.093moles/L*0.02938L=0.002732moles
moles of acetylcylicylic acid=moles of NaOH=0.002732moles (since they react 1:1)
mass of acetylcylicylic acid=moles*molar mass
=0.002732moles*138.12g/mole=0.3774g=377.4mg
2.) Students working in lab accidentally spilled 2.8 L of 3.0 M H2SO4 solution. They find a large container of acid neutralizer that contains baking soda, NaHCO3. How many grams of baking soda will be needed to neutralize the sulfuric acid spill? My Answer: 1411.3 g
Moles of H2SO4=3.0moles/L*2.8L=8.4moles
H2SO4 + 2NaHCO3 ==>Na2SO4 + 2H2O + 2CO2
since they react in (2:1)
moles of NaHCO3=2*moles of H2SO4=2*8.4=16.8moles
mass of NaHCO3=moles*molar mass=16.8*84g/mole=1411.2g
3.) A powder contains benzoic acid mixed with starch. A student finds that a 4 g sample of this powder requires 35.01 mL of a 0.095M sodium hydroxide solution for the acid to be neutralized. What is the percent by mass of benzoic acid in the powder? My Answer: 10.15%
Moles of NaOH=0.095moles/L*0.03501L=0.003326moles
moles of Benzoic acid=moles of NaOH=0.003326moles (since they react1:1)
mass of benzoic acid=moles*molar mass=0.003326moles*122.12g/mole=0.4062g
mass %age of benzoic acid in sample=mass of benzioc acid/mass of sample*100
=0.4062g/4.0g*100=10.15%
4.) Barium oxalate is used as a colorant to produce the green color in fireworks. Imagine that you have been assigned to prepare barium oxalate by reacting barium hydroxide octahydrate (Ba(OH)2