Chem 160 written lab practical review
Chem 160 written lab practical review
What type of mixture are you given in experiment 1? (Copper (II) sulfate and Salicylic Acid) - ANSWER
heterogeneous mixture
In experiment 1, Dissolving both compounds in the mixture is the first step in the experiment. What
solvent works best for this? - ANSWER hot water (can dissolve both compounds)
what does the bunsen burner barrel do? - ANSWER adjusts the amount of air going into the burner
what does the valve on the bottom of the bunsen burner do - ANSWER adjusts amount of natural gas
going into the burner
Which flame is hotter: yellow or blue? - ANSWER blue is a hotter flame then yellow
What is the correct flame appearance when heating something - ANSWER visible outer and inner "cone"
of blue flame
What is the hottest portion of the flame? - ANSWER the top of the inner "cone" of the blue flame
In experiment 1, once both compounds in the mixture are dissolved, what must be done to precipitate
out one of them as a solid and which compound precipitates? - ANSWER 1. you most cool the solution in
an ice/water bath to precipitate one of the compounds
2. From the ice bath, the Salicylic acid precipitates
In experiment 1, how do you isolate this first solid? How do you isolate this first solid? If some of the
solid remains stuck in the beaker, how can you get it out without changing the amount you isolate? -
ANSWER 1. you isolate the first solid by gravity filtration
2. To remove solid from the beaker, you can wash it with cold or lukewarm water because this
compound is only soluble in hot water
, Chem 160 written lab practical review
Which compound remains dissolved in solution after the first compound is isolated as a solid? What are
the next two steps that you must take in order to precipitate this second compound out of solution? -
ANSWER The compound that remains in solution is copper(II) sulfate pentahydrate. To precipitate it, you
must first evaporate most of the solution water off then add ethanol.
After you have isolated both compounds, separately, from your mixture, why do you wait a week before
weighing them? - ANSWER There is still residual liquid on the solids that must evaporate - the extra
week provides the time for this to happen.
Why is salicylic acid more soluble in ethanol than CuSO4 5 H2O? - ANSWER salicylic acid is an organic
compound and more soluble in ethanol
In experiment 1, if you recover less than the original mass of your sample mixture, choose two things
that could have happened to the "missing" amount? - ANSWER 1. did not precipitate out of solution
completely
2. residual precipitate was not completely removed from the beaker to the filter
Geoffrey the General Chemist used 2.498 g of a mixture of CuSO4 5 H2O and salicylic acid in this
experiment. He recovered 1.324 g of salicylic acid and 1.247 g of CuSO4 · 5 H2O. What is his percent
recovery? - ANSWER 102.9%
What is wrong with Geoffrey's result of 102.9%? - ANSWER it is above 100%
How could Geoffrey's 102.9% recovery from above have been avoided? - ANSWER by further drying the
sample
Geoffrey used 2.498g of the original mixture and recovered 1.324g of salicylic acid. What is the percent
recovery from the original mixture? - ANSWER 53%
Geoffrey used 2.498g of the original mixture and recovered 1.247 of CuSO4 5H2O. What is the percent
recovery of the Copper (II) sulfate? - ANSWER 49.92%
Chem 160 written lab practical review
What type of mixture are you given in experiment 1? (Copper (II) sulfate and Salicylic Acid) - ANSWER
heterogeneous mixture
In experiment 1, Dissolving both compounds in the mixture is the first step in the experiment. What
solvent works best for this? - ANSWER hot water (can dissolve both compounds)
what does the bunsen burner barrel do? - ANSWER adjusts the amount of air going into the burner
what does the valve on the bottom of the bunsen burner do - ANSWER adjusts amount of natural gas
going into the burner
Which flame is hotter: yellow or blue? - ANSWER blue is a hotter flame then yellow
What is the correct flame appearance when heating something - ANSWER visible outer and inner "cone"
of blue flame
What is the hottest portion of the flame? - ANSWER the top of the inner "cone" of the blue flame
In experiment 1, once both compounds in the mixture are dissolved, what must be done to precipitate
out one of them as a solid and which compound precipitates? - ANSWER 1. you most cool the solution in
an ice/water bath to precipitate one of the compounds
2. From the ice bath, the Salicylic acid precipitates
In experiment 1, how do you isolate this first solid? How do you isolate this first solid? If some of the
solid remains stuck in the beaker, how can you get it out without changing the amount you isolate? -
ANSWER 1. you isolate the first solid by gravity filtration
2. To remove solid from the beaker, you can wash it with cold or lukewarm water because this
compound is only soluble in hot water
, Chem 160 written lab practical review
Which compound remains dissolved in solution after the first compound is isolated as a solid? What are
the next two steps that you must take in order to precipitate this second compound out of solution? -
ANSWER The compound that remains in solution is copper(II) sulfate pentahydrate. To precipitate it, you
must first evaporate most of the solution water off then add ethanol.
After you have isolated both compounds, separately, from your mixture, why do you wait a week before
weighing them? - ANSWER There is still residual liquid on the solids that must evaporate - the extra
week provides the time for this to happen.
Why is salicylic acid more soluble in ethanol than CuSO4 5 H2O? - ANSWER salicylic acid is an organic
compound and more soluble in ethanol
In experiment 1, if you recover less than the original mass of your sample mixture, choose two things
that could have happened to the "missing" amount? - ANSWER 1. did not precipitate out of solution
completely
2. residual precipitate was not completely removed from the beaker to the filter
Geoffrey the General Chemist used 2.498 g of a mixture of CuSO4 5 H2O and salicylic acid in this
experiment. He recovered 1.324 g of salicylic acid and 1.247 g of CuSO4 · 5 H2O. What is his percent
recovery? - ANSWER 102.9%
What is wrong with Geoffrey's result of 102.9%? - ANSWER it is above 100%
How could Geoffrey's 102.9% recovery from above have been avoided? - ANSWER by further drying the
sample
Geoffrey used 2.498g of the original mixture and recovered 1.324g of salicylic acid. What is the percent
recovery from the original mixture? - ANSWER 53%
Geoffrey used 2.498g of the original mixture and recovered 1.247 of CuSO4 5H2O. What is the percent
recovery of the Copper (II) sulfate? - ANSWER 49.92%
