I need help with question 1 a b and 2 for chemistry. I need your help. Thanks th

Question

I need help with question 1 a b and 2 for chemistry. I need your help. Thanks
the second image is all the step 1 to 10

Chemistry 161 Lab2 Fall 2017, Bozlee, based on S. Critchlow page 5 of 9 Analysis Questions (You may print this page and write your responses by hand, or type and print the responses.) a) In step 5, when the student weighed the pycnometer filled with water, there were several large drops of water on the outside he failed to dry off. Will his calculated volume of the pycnometer be high, low, or the same as the true value? Explain your reasoning. 1. b) With this error in step 5, will his calculated density of his unknown isopropanol solution found in step 8 (if proper technique is used in step 8) be high, low or unaffected? Explain your reasoning. a) Jn my opinion,I hinlz tha volume ihe pycnomete when the en as cocuaton will be fou as tua value 2. Another student weighed her empty dry pycnomete r once in step 2, but did not follow instructions and reweigh her empty pycnometer in subsequent steps, instead using her original empty weight. Because of this, in step 9, she failed to notice that there was remaining in the pycnometer when filling it with the pure isopropanol and weighing it. With this error, will her calculated density determined for the pure isopropanol be high, low, or unaffected? Explain. (Hint, look up the density of acetone!). acetone

Explanation / Answer

1a) The weight of water used to fill the pyenometer completely can be obtained by subtracting the weight of the empty, dried pyenometer from the weight of the filled pyenometer. Dividing this weight difference by the known density of water gives the volume of water required to fill the pyenometer. By convention, this volume is taken to be the volume of the pyenometer.

When there are large drops on the outside of the pyenometer, the weight of the filled pyenometer will be higher than the actual weight and hence, the weight difference = (pyenometer + water) – (empty dried pyenometer) will be much higher than the true value. Dividing this weight difference by the fixed density of water will result in the volume of the pyenometer being too high.

b) The density of isopropanol is given as (mass of isopropanol required to fill the pyenometer completely)/(volume of pyenometer). The volume of the pyenometer was calculated high in part (a) above. However, the weight of isopropanol required to fill the pyenometer completely is fixed; hence, dividing this fixed weight by a high volume will result in the calculated density of the isopropanol being too low.

2) The density of isopropanol and acetone are more or less similar, around 768 kg/m3. The volume of the empty dried pyenometer is fixed and hence, the pyenometer can only take in a fixed weight of the liquid. Since there was some acetone in the pyenometer from before, the volume of isopropanol required to fill the pyenometer will be low. However, the mass and the volume of the pyenometer remaining unchanged, the density of the pure isopropanol will be unaffected due to the presence of acetone.

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