INTRODUCTION:

In this experiment you will carry out a chemical reaction and determine the balanced chemical equation for the reaction. You will make use of the fact that the coefficients of the reactants and products in a chemical equation represent the relative number of moles of each reactant and product involved in the reaction. You will determine the relative numbers of moles of each reactant and product in the reaction you observe. From these mole ratios, you will derive the appropriate coefficients to be used in the chemical equation.
Specifically, you will allow iron metal to react with a solution of copper(II) chloride, to produce copper metal and an iron compound. You will measure the mass of the iron used and the copper formed in the reaction. Using these mass measurements, you will determine the number of moles of iron and copper involved in the reaction. The ratio of moles of iron consumed to moles of copper produced will be used to determine the proper coefficients for the chemical equation of the reaction.

MATERIALS:

Safety goggles
250-ml beaker
any size beaker
50-ml graduated cylinder
stirring rod
wash bottle
Tongs or tweezers
Steel wool
2 iron nails, Fe
Copper(II) chloride dihydrate, CuCl₂ * 2H₂O
25 ml of 1 molar hydrochloric acid, HCl
distilled water
Balance
Weighing dish or paper

CAUTION: Always wear your safety goggles!

Remember that hydrochloric acid is corrosive and acts like bleach on clothing. Copper(II) chloride is an irritant.

PRE-LAB PREP:

You should be able to buy a 1 molar concentration solution of hydrochloric acid. If not, mix 2.2 ml of concentrated acid with enough distilled water to make a total volume of 25 ml. (REMEMBER: NEVER ADD WATER TO ACID, ALWAYS ADD ACID TO WATER)

PROCEDURE:

DAY 1

1. Take your clean, dry 250-ml beaker and find the mass of the beaker to the nearest 0.01g and record the mass on the DATA TABLE.

2. Using the weighing dish or paper, and the proper procedure for the balance used, weigh out 7.50g of copper(II) chloride dihydrate, CuCl₂ * 2H₂O. Record this mass on the DATA TABLE.

3. Transfer the copper(II) chloride sample to the 250-ml beaker, and add 50 ml of distilled water. Be sure to use some of the 50 ml of water to rinse the weighing dish into the beaker. Stir or swirl the mixture until the crystals are completely dissolved. If you used the stirring rod, rinse it off into the beaker with a small amount of distilled water so no chemical is lost.

4. Clean 2 dry iron nails with steel wool to remove any rust or protective coating. Place the nails on the balance pan and determine their combined mass to the nearest 0.01g. Record this mass on the DATA TABLE.

5. Slide the nails carefully into the solution of copper(II) chloride. Place the beaker in a safe location and allow it to react for 24 hours. Observe the reaction for a few minutes.

DAY 2

6. Using the tongs or tweezers, carefully remove the nails one at a time, from the reaction beaker and using a jet of water from a wash bottle to rinse the adherent reaction product off the nails into the beaker.

7. Place the nails on a paper towel and set aside to dry over night.

8. Carefully pour the liquid portion of the remaining mixture in the reaction beaker into a collection container (the other beaker), leaving the solid reaction product in the original beaker. This process is called decanting. Dispose of the decanted solution by pouring it from the collection beaker.

9. Wash the reaction product in the reaction beaker with 25 ml of distilled water. Let it settle, and decant the wash water into the collection container. Repeat the washing and decanting procedures another three times, being careful to avoid any loss of reaction product.

10. Now wash the remaining product with 25 ml of 1molar hydrochloric acid. Decant the acid wash as before. Wash the solid again with 25 ml of distilled water and decant as before. (The acid wash can be omitted, but makes the results more accurate)

11. Place the beaker in a safe place to allow the copper sample to dry completely.

DAY 3

12. Find the combined mass of the 2 dry nails to the nearest 0.01g. Record the mass on the DATA TABLE, as mass after reaction.

13. When the copper sample is completely dry, find the combined mass of the beaker and copper sample to the nearest 0.01g and record it on the DATA TABLE.

DATA TABLE:

Mass of one mole of Iron, Fe (atomic weight in grams). 55.85 g

Mass of one mole of copper, cu (atomic weight in grams). 63.55 g

Mass of the empty 250-ml beaker. __________ g

Mass of the copper(II) chloride dihydrate sample. __________ g

Mass of the 2 iron nails before reaction. __________ g

Mass of the 2 iron nails after reaction. __________ g

Mass of the beaker and copper sample. __________ g

CALCULATIONS:

14. Calculate the mass of iron lost by the nails.
This is the mass of the iron nails before reaction - after reaction.

15. Calculate the number of moles of iron used.
This is the number of grams from step 14 divided by the mass of one mole of iron.

16. Calculate the mass of copper produced.
This is the combined mass of beaker and copper, minus the mass of the empty beaker.

17. Calculate the number of moles of copper produced, just as you did for the iron.

18. Calculate the mole ratio if iron used to copper produced. This is done by dividing the number of moles of iron by the number of moles of copper (moles Fe / moles Cu ). Express your answer as a decimal, and then write the simple whole number ratio. Remember, the bottom number in the division becomes 1 in the simple ratio. This is the copper. Your decimal answer is for the iron, and you simply round it to the nearest whole number.

WHOLE NUMBER MOLE RATIO

mole Cu : mole Fe

___1___ : _______

___ Fe + ___ CuCl₂ --> ___ Cu + ___ FeCl₂