Chemistry: Ch. 7 lab. Calculating the zinc in galvanized steel Do not write on this! Return to teacher.

Materials

1 galvanized steel strip250 mL beaker3 Molar hydrochloric acid goggles and apron

Warning

Hydrochloric acid is corrosive! Be sure to wear goggles and apron when using the acid. Wash any areas that come in contact with acid with water. In case of eye contact use the eyewash immediately.

Procedure

1.Create a data table for the following information on your own paper

Mass of galvanized strip in grams
Length of metal strip in cm, Width of metal strip in cm
Mass of iron in grams

2. Mass the galvanized metal strip and record in the data table.

3.Use a ruler to find the length and width of the metal strip to the nearest 0.1 cm and record in the data table.

4.Bend the strip into a V shape and place on edge in the bottom of a 250 mL beaker

5.Carefully pour 3 molar hydrochloric acid in the beaker until the strip is well covered. Both sides of the strip should be exposed to the acid.

6.When the bubbling stops, gently let tap water flow into the beaker and out into the sink to dilute any remaining acid.

7.Recover the metal strip from the beaker and dry.

8.Mass the reacted metal strip and record in the data table as mass of iron

Calculations

Do the following calculations on your paper, showing work with units and circling the result of each calculation.

1.Calculate the mass of zinc removed by the hydrochloric acid

2.Calculate the percentage by mass of iron and zinc in the galvanized metal strip.

3.Find the volume of the iron and zinc in the strip in cm3 using the masses of each metal and the density of

each metal from your periodic table.

4.Find the percentage by volume of iron and zinc in the galvanized metal strip.

5.Calculate the surface area of one side of the metal strip in cm2.

Calculate the thickness of the zinc in cm using the volume of zinc. Since the strip was coated on both sides

the relationship is volume of zinc = 2 x (thickness x surface area of one side of strip).

6.Calculate the thickness of the iron in cm using the volume of iron.

The relationship is volume of iron = (thickness x surface area of the strip).

7.Calculate the percentage of the total strip thickness that is due to the zinc.

8.Calculate the number of moles of iron and zinc in the galvanized strip.

9.Find the percentage of the total atoms in the metal strip that are zinc and that are iron. The percentage of the

atoms will be equal to the percentage of moles.

Questions

Answer the following questions on your own paper

1.Write a balanced chemical equation for the reaction of the zinc metal with hydrochloric acid.

2.Which has a higher chemical activity zinc or iron?

3.Which metal reacts more readily with oxygen gas? Write the formulas for iron (III) oxide and zinc oxide.

4.Why do they coat the steel with zinc?

5.Old galvanized metal has a layer of white powder on the surface. What is the white powder?

6.Why did they leave the green coating on the copper surface when they cleaned the Statue of Liberty?