Chem 131- Post Lab 1 - The questions and answers for post lab. PDF

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The questions and answers for post lab....

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Post Lab Assignment – Measurements in the Laboratory CHEM 131L Include the following information at the top of the first page of your assignment: Name: Julianna Zor Lab Partner(s): Jenny Lucas & Chris Wiley Lab Section Number: 03 Experiment Title: Measurements in the Lab Sept 13, 2017

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GENERAL INSTRUCTIONS The entire report should be typed (handwritten portions will NOT be graded). Please organize your report as shown below. You and your lab partner may not turn in the same work. Be sure to report all values to the correct number of significant figures and with appropriate units. Questions and Calculations 1. Station 1 1. List the two measurements made at this station with correct labels, units and significant figures. Which was more accurate measurement and why? Briefly explain. One measurement is 6.4 mL in a 10 mL and the other is 46.5 mL in a 50mL. The 50mL cylinder was more accurate because it was easiest to read. However, to be sure the percent error could be calculated. To find the percent error we would need the actual value. 2. What is the name of the piece of glassware used to make these measurements? The glassware is called a graduated cylinder. 2. Station 2 1. Calculate the mass of the metal sphere. Report the final answer to the correct number of significant figures with units. Show the typed calculation to receive full credit. 18.778 g – 4.876 g = 13.90 g

2. The known mass of the sphere is 13.878 g. Calculate the percent error in your measured mass. Show the typed calculation to receive full credit. 13.90g – 13.878g / 13.878 g = 17.408 g 3. Station 3 1. Calculate the perimeter (A+B+C = perimeter) of the triangle in units of meters. Report the final answer to the correct number of significant figures with units. Show the typed calculation to receive full credit. 10 dm = 1 m 6.5 dm / 10= .65 m 100 cm = 1 m 75 cm / 100 cm= .75 m 1000 mm = 1M 41.3mm / 1000 mm= .0413 mm .65 m + .75 m + .0413 m= 1.4413 m 1.4 m 2. How would you change the measurement process to obtain a perimeter value with more significant figures? First, with addition significant figures goes by the least amount of places to the right of the decimal. If we wanted more significant figures we would need to convert the length, width, and height to different units with more numbers after the decimal point. 4. Station 4 1. Report the label on the block you measured in lab. Calculate the density of the block. W-5 D= M/V

D= 104.10g/(4.7mm x 8mm x 5.5 mm) D= 104.10g / 206.8 mm D= .5034 g/mm^3 2. If the mass of the block had been measured on a balance that reads to four decimal places, would that have changed the density value reported above? Briefly explain why or why not. No, it would not have changed the density value because the mass we measured was already four significant figure....