Lab Partner(s): Day aaaa.

Transcription

1 Experiment: The Mole Last Name First Lab Partner(s): Day aaaa. Objective In this experiment, students use nuts (N) and bolts (B) as model elements to build model compounds using these elements. Calculations are performed to identify unknown compounds and to quantify a known compound. These calculations mirror the process for using molar mass to calculate the number of moles of a substance. This process is then applied to a mixture of lentil beans and to some common substances. The goal is to obtain a deeper functional understanding of the mole concept and its use. Materials In Bin o Bag of screws o Bag of Lentils & Beans o Bag of bolts o Unknowns in conical vials In Room o Alloy cube o Sugar packet o Distilled water o Balance Introduction Required additional reading: Ch 7.4 the Mole and 7.5 Molar Mass in Chemistry in our Lives Timberlake 5 th Edition. pppp. 67

2 Procedure Part I. Establishing the mass of individual elements and molecules. These are found in the clear container. Open the container to remove the 10 HexNuts and 10 Bolts. A. Element #1 (the HexNut) and Element #2 (the Bolt) Determine and record the following information: i) The average mass of a single HexNut to the precision of the scale. The best way to measure the average mass of a HexNut is to weigh 10 HexNuts and divide the total mass by 10. Show your work here. Ai) g ii) The average mass of a single Bolt to the precision of the scale. As mentioned above, the best way to measure the average mass of a bolt is to weigh 10 bolts and divide the total mass by 10. Show your work here. Aii) g Calculations: B. Compounds #1 (BN), #2 (BN2), #3 (BN3) and #4(BN4): Bolt HexNut molecules The combined Bolt (B) and HexNut (N) "elements" will represent our theoretical "compound" and will be represented by BN, BN 2, BN 3 and BN 4. Weigh the container with the compound. Subtract the mass of the container, calculate and record the average mass of the following Bolt-HexNut compounds. Show your calculation of the average mass in the right-hand column. NAME Average Mass Calculations BN Bi) g BN BN2 Bii) g BN2 BN3 Biii) BN3 BN4 Biv) BN4 68

3 C. The Lentil-Beans LB 5 These are found in the plastic baggies labeled LB 5. Do NOT open this container. i) Weigh the container containing the 20 Lentil-Beans and record the gross mass in line Ci. Ci) g (gross) ii) Record the mass of the container in line Cii. This mass is written on the label Cii) g Mass of container iii) Subtract the mass of the container from the gross mass and write the net mass in line Ciii. Ciii) g 20 LB 5 (net) iv) Calculate the mass of one-lentil-bean (LB 5 ) based on the data collected. Civ) g Average Mass of LB 5 Calculations: 69

4 Part 2. Counting by Weighing. In this part of this lab, you will determine the number of elements or compounds in a sealed container by weighing the container and its contents and then using the information from part I, you will calculate the number of elements or molecules. D. The number of HexNuts in a container This unknown is found in the green container. Do NOT open this container. i) Record the mass of the unknown HexNuts, (Element #1). ii) Record the mass of the container as written on the label of the container. iii) Calculate and record the net mass by subtracting the mass of the empty container from the gross mass measured. iv) Using the average mass of a single HexNut from Part I, calculate the number of HexNut elements in your unknown. Show your calculations below. Your answer must be a whole number. D i) g Mass of Container+ HexNut (gross) D ii) g Mass of Container (label on Container) D iii) g Mass of HexNut in container (net) D iv) number of HexNut in container Calculations for D iv. E. The number of molecules (BN) in a container This unknown ais found in the orange container labeled Unknown (BN). Do NOT open this container. Look for the container containing BN items. i) Record the mass of container 2 in line Ei. This is the BN molecules plus the container. ii) Record the mass of the container as written on the label of the container in line Eii. iii) Calculate the net mass by subtracting the mass of the empty container (as written on the container) from the gross mass measured. Write this mass in line E iii. iv) Using the average mass of a single BN compound, calculate the number of BN compound in your unknown and write this value in line E iv. Show your calculations below. Your answer must be a whole number. E i) g Mass of container + BN (gross) E ii) g Mass of container (label on Container) E iii) g Mass of BN in container (net) E iv) number of BN compounds in container Show Calculations on facing page. 70

5 F. The number of molecules (Lentil-Bean, LB 5 ) in a container This unknown is found in the purple container labeled Unknown (LB 5 ). Do NOT open this container. i) Record the mass of container #3 in line Fi. This is the Lentil-Bean molecules plus the container. ii) Record the mass of the container as written on the label of the container in line F ii. iii) Calculate and record net mass of the LB 5 in line F iii. F i) Mass of container + LB5 (gross) F ii) Mass of container (written on label) F iii) Mass of LB5 (net) iv) Using the average mass of a single LB 5 compound, calculate the number of LB 5 compound in your unknown and write this value in line F iv. Show your calculations in the below. Your answer must be a whole number. F iv) number of Lentil-Bean in container Calculations for F iv. Calculations for E iv. 71

6 Part 3. Identification of an Unknown based on Average Mass. G & H: Determining the identity of the compound (BN, BN2, BN3 or BN4) These are found in the Blue (G) and Yellow (H) containers labeled Unknown (BN n ). Do NOT open these containers. Part G Part H i) Record the number of molecules as written on the containers for this part. Write these in line Gi and Hi. G i) # of molecules H i) # of molecules ii) Weigh each container and record the mass in line Gii and Hii. G ii) g Mass of container + Unknown (gross) H ii) g Mass of container + Unknown (gross) iii) Record the mass of each container as written on the label of the containers. Write the mass of each container in lines Giii and Hiii. G iii) g Mass of container H iii) g Mass container iv) Calculate the net mass of the content in each container. G iv) g Mass of Unknown1 (net) H iv) g Mass of Unknown2 (net) v) Take the net mass and divide by the total number of molecules. This is the average mass of a single molecule in the container. Show your calculations below. vi) Using the data for the average mass of the BN, BN 2, BN 3 and BN 4 from part 1B, identify the chemical formula of your unknown in the container for this part. Calculations for Gv and Hv. G v) g Average mass of Unk 1 G vi) Formula of molecule in container H v) g Average mass of Unk 2 H vi) Formula of molecule in container 72

7 Part 4. Calculations, Converting from Mass to Moles for some common objects. Using the mass of the iron cube, the 50.0mL of water and the packet of sugar, determine the number of moles of metal, water and sugar. Round of to correct number of significant figures and use scientific notation when appropriate. I. The number of moles of Fe in a cube i) Metal cube: Weigh a metal cube and write the mass in line I i. I i) g Fe ii) Write the average atomic mass of Iron iii) Calculate the number of moles of the metal in the cube and write your answer in line I ii. (Show calculations below using dimensional analysis) I ii) g/mole I iii) moles of iron iv) How many iron atoms are in the cube? Calculations for Table I. I iv) atoms of iron 73

8 J The number of moles of water in 50.0 ml of water i) 50.0 ml of water: Tare a 50mL-graduated cylinder on the scale. Add water and bring to precisely 50.0mL of water using a Berel pipet. Weigh the graduated cylinder with the water and record the mass. i) g 50.0 ml water ii) Add up the molar mass of water and write your answer to the right. ii) g/mole for water iii) Calculate the number of moles of water in the 50- ml volume of water. Show your calculations below. iii) moles of water Move to Next Table answer questions below as a Post Lab iv) Calculate the number of water molecules in 50.0 ml. Show your calculations below. iv) molecules of water v) Calculate the number of Oxygen and H atoms in 50 ml of water. Show your calculations below. Calculations for Table J v) O atoms in water H atoms in water 74

9 K. The number of moles of sucrose in a packet of sugar i) Packet of sucrose (sugar), C12H22O11: Weigh a packet of sugar and record the gross mass of the i) g mass of sugar + bag (gross) sugar packet. ii) Read and record the mass of the container from the label of the packet. ii) g mass of bag iii) Calculate the mass of the sugar in the packet and record in line Kiii. iii) g mass of sugar (net) iv) Calculate the molar mass of sucrose (C12H22O11 ). Show your calculations below. iv) g/mole v) Calculate the number of moles of sucrose in the packet. Show your calculations below. v) moles of sugar Answer questions below as a Post Lab vi) Calculate the number of molecules of sucrose in the packet of sugar. Show your calculations below. vi) molecules of sugar vii) Calculate the number of atoms of C, H, and O in the packet of sugar. Show your calculations below. Clean up - Replace all items in your bin and bring back to the cart. Complete calculations for table K vii) C atoms H atoms O atoms 75

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