Chemical reactions -a quantitative investigation.

Part A
 

Part A

Copper metal => copper ions + nitrogen dioxide + water

Cu (s) + 4HNO3 (aq)--> Cu(NO3)2(aq) + 2NO2 (g) +2H2 O (l)
  

 

Step 1 Label a 250 mL beaker and label it with your name. Record the mass of the beaker in the table below.

 

Step 2 Add to the beaker approximately 1.50 grams of copper metal and reweigh. Record the mass of the beaker and copper to 2 decimal places and fill in the table below.

  

 
Step 3 In the fume cupboard measure 15.0 mL of 7M nitric acid and place it in the beaker with the copper metal. Place a watch glass on top of the beaker. You will notice a brown gas being produced. This is nitrogen dioxide and it is poisonous and very corrosive. Click to see a 400 kB video.  

 
Step 4 Leave the beaker in the fume cupboard until no further reaction is observed.  
Mass of 250 mL beaker  
Mass of 250 mL beaker and copper metal.  
Mass of copper metal at the start  

1) How do you know that a chemical reaction is taking place?

2) What makes the solution blue?

3) Does the reaction involve energy? Explain.