CH 102 Lab 1 PostLab

32 kernels in 30 seconds

(a) What is the average rate at which the student counted popcorn kernels?

1.067 kernels/second or 0.938 seconds/kernel

(b) Using the answer above as a conversion factor, determine the time, in seconds, that it would take to count one mole of kernels.

b) 5.649e23 s

(c) Using the following conversion factors, calculate the number of years it would take to count one mole of kernels.
60 seconds = 1 minute 60 minutes = 1 hour 24 hours = 1 day 365 days = 1 year

1.791e16 yr

(d) If you had started counting one mole of kernels when the earth was formed, would you be finished by now? (Hint: The age of the earth is about 4 billion (4 ✕ 109) years.)

No

(e) Choose the most efficient and accurate way to prepare a sample containing 0.75 moles of iron (Fe) atoms.

Weigh 41.89 grams of iron.

In lab you determined the average masses of popcorn kernels and marbles. One student got the following results. Your values should have been similar.

Item: one dozen popcorn kernels Average Mass: 1.644 g
Item: one dozen marbles
Average Mass 51.960 g

Use this student's results to answer the following questions.

(a) What is the mass of one popcorn kernel?

0.1370 g

(b) What is the mass of 4.25 dozen popcorn kernels?

6.987 g

(c) How many popcorn kernels are in a sample that has a mass of 53.567 g?

391.0 kernels

(d) What is the mass of one marble?

4.3300 g

(e) What is the mass of 4.25 dozen marbles?

220.83 g

(f) What is the relative mass of a single marble to a single popcorn kernel? (Sig Fig Hint: Consider the precision of the masses of one kernel and one marble to determine the correct number of sig figs.)

31.61

Using Avogadro's number, 6.02 ✕ 10^23 things/mole, answer the following questions. (Use scientific notation for large answers.)
(g) What is the mass of one mole of popcorn kernels?

8.25e22 g

(h) What is the mass of one mole of marbles?

2.61e24 g

(i) What is the relative mass of one mole of marbles to one mole of popcorn kernels

31.6

(j) The relative mass of a single marble to a single popcorn kernel is ___ the relative mass of a mole of marbles to a mole of popcorn kernels.

equal to

Part B Continued: Atomic Molar Masses

Atoms of different elements also have different average masses, just like kernels and marbles. Use the mass values from a periodic table to answer the following questions. Please use the precision of the values in the periodic table link to determine the correct number of significant figures for your answer.

(a) What is the relative mass of one atom of Be to one atom of N?

0.6433

(b) What is the relative mass of one mole of Be to one mole of N?

0.6433

(c) What is the relative mass of 1.3 moles of Na to 1.3 moles of Ag?

0.2131

Part C: Volume, Mass, Density, and Moles

In lab you determined the volume of 12 marbles and the mass of 18.0 mL of water. Use the following data, which should closely approximate your results, to answer the questions below.

Mass of 18.0 mL of water: 18.0 g
Mass of 12 marbles (from postlab Part B): _______
Volume of 12 marbles: 22.3 mL

51.960 g

(a) What are the densities determined from the data above? (Sig Fig Hint: Use the precision of the mass of water and volume of marbles to determine the correct number of significant figures for all answers.)

water:
marbles:

water: 1.00
marbles: 2.33

(b) The number of moles of water present in 18.0 g of water is ________

1.00 mol

(c) Use scientific notation for the number of water molecules in 18.0 g of water. (Enter your answer using the format 2.2e21 for 2.2 ✕ 1021.)

6.02e23

(d) What is the mass of a single molecule of water?

2.99e-23

(e) How many water molecules would have the mass of one marble?

1.45e23

(f) Neglect empty space between molecules and calculate the average volume of a water molecule.

2.99e-23

(g) What is the average volume of a marble?

1.86

(h) How many water molecules could fit in the same volume as one marble?

6.22e22

Atoms of different elements also have different sizes, just like kernels and marbles. Use the atomic radii given below to answer the following questions. Remember that the volume of a sphere is
4
3
× 𝜋 × radius3.
Please use the precision of the radii in the table to determine the appropriate number of significant figures for the answers.
(a) What is the volume of one atom of N?

1.4 A3

(b) What is the volume of one atom of Rb?

63.9 A3

(c) How many N atoms are needed to occupy the same volume as a Rb atom? (Please add one additional significant figure to the values in parts (a) and (b) before calculating the value for part (c). This is the proper procedure for handing significant figures and avoiding errors from early rounding.)

44.36