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Stoichiometry

PROCEDURE:

1) The lab has been recorded as the directions that follow: Record the mass of the empty beaker and paper cup.

2) Drag the copper(II) sulfate containing spoon to a position directly above the beaker and press the “p” key. The copper(II) sulfate sample will be dropped into the beaker. Use the balance to determine the combined mass of the beaker and copper(II) sulfate sample. Record this value.

3) Fill the beaker about 2/3 full with water from the faucet. Place the beaker on the hot plate and turn the hot plate on. Slide the red temperature lever, in the front, to about 2/3 of the way to the right. Copper(II) sulfate will dissolve in water on its own but our large crystal sample would take too long. Heat speeds up the dissolving process. Note any color change in the water.

4) Drag the Fe bearing spoon so it is directly above the paper cup and press “p” to dump the Fe in the cup. Determine the combined mass of the paper cup and Fe sample and record.

5) Place the hot beaker on the table. Drag the paper cup (containing the Fe) so that the left corner of the paper is centered over the opening in the beaker. Press “p” to dump the Fe into the beaker. Note any changes in the beakers contents.

6) The Fe and copper(II) sulfate have fully reacted and Cu has been released. Iron(II) sulfate has also been produced but has dissolved in the water and cannot be seen. Some excess copper(II) sulfate is also dissolved in the water.

7) Hold the beaker over the sink and press “p” to pour out all of the unwanted water and compounds. Fill the beaker about 1/4 full and dump into the sink by pressing “p”. Repeat. This washes out any unwanted materials from our copper metal. Note that due to the higher density of the copper, it remains in the beaker.

8) Place the beaker on the warmed hot plate and heat for a short time. This drives off any left overwater. Mass the beaker containing the copper and record.

6) Calculate the requested values asked for on the lab sheet.

Stoichiometry Lab

Assistance with the lab:

1. To find a chemical formula, NaCl for example, look it up on the internet or your book.

2. To calculate moles (mol) for Na, first look up atomic weight of sodium (Na) on periodic table or internet, 22.99

Next calculate mass of Sodium chloride (NaCl), Na atomic weight 22.99 and Cl atomic weight 35.45, add them together 22.99 + 35.45 = 58.44 g.

Now, 22.99g/58.44g = 0.3933 mol Moles = mass/atomic mass.Error = O – A 4. % Error = error/ A x 100

Use the blue button that says Special for help too. This button is on top left of your lab page when signed into your lab.

Mass Cu (g): _____ Observed value (O)

Observations: When heating the CuSO4: you should have noted that the lump of CuSO4 decreased while heating and the solution became a darker blue color (more dissolved CuSO4).

After the Fe was added to the CuSO4 solution: the student should have noted that the lump of Fe disappeared, the solution decreased in blue color and the copper metal appeared.

From Calculations

Moles of CuSO4 = grams of CuSO4 / atomic mass of CuSO4 = ________ mol (Excess Reactant)

Moles of Fe = grams of Fe / atomic mass of Fe =_________ mol (Limiting reactant)

Balanced equation: CuSO4 + Fe —– Cu + FeSO4

Ratio of reactant Fe to product Cu = 1:1

role ration for equation = mol of Fe / coefficient of Fe = mol of Cu / coefficient of Cu

= _____/1 = unknown Cu/1

unknown Cu = _____ mol

Mass of Cu = mol of Cu x atomic mass of Cu

= ______ g (Accepted value)

Error = O – A

= ____ g

% Error = Error / A x 100