E3 Reactions of copper

Predict the effect on calculated % yield.

The precipitate was weighed even if traces of red brick solids are present

• Increase

• Decrease

• No effect

• Indeterminate

Answer explanation

Cu metal (red precipitate) weighs less than CuO (MW of Cu is lower than CuO).

Predict the effect on calculated % yield.

Addition of H2SO4 was stopped even there are still black precipitate in the filter paper

• Increase

• Decrease

• No effect

• Indeterminate

Answer explanation

Not all CuO was converted to CuSO4.

Predict the effect on calculated % yield.

Litmus paper did not change to blue when moistened with supernatant.

• Increase

• Decrease

• No effect

• Indeterminate

Answer explanation

Incomplete precipitation of Cu(OH)2 due to insufficient amount of NaOH added to Cu(NO3)2.

What is the compound in [1]?

What is the reagent in [4]?

What is the compound in [5]?

What is the answer in [6]?

What is the color of the solution after addition of H2SO4?

What is the answer in [8]?

[9] What is the product when the reaction is complete?

• [Zn(NH3)2]^2+

• [Zn(NH3)4]^2+

• [Cu(NH3)4]^2+

• [Cu(NH3)4]^+