Please help, and if you could also give me a step by step that would be awesome!!

4.4 g

Explanation:

Step 1: Write the balanced equation

Cu + 4 HNO₃ ⇒ Cu(NO₃)₂ + 2 NO₂ + 2 H₂O

Step 2: Calculate the moles corresponding to 3.2 L of NO₂ at STP

At standard temperature and pressure, 1 mole of NO₂ occupies 22.4 L.

3.2 L × 1 mol/22.4 L = 0.14 mol

Step 3: Calculate the moles of Cu needed to produce 0.14 moles of NO₂

The molar ratio of Cu to NO₂ is 1:2. The moles of Cu needed are 1/2 × 0.14 mol = 0.070 mol.

Step 4: Calculate the mass corresponding to 0.070 moles of Cu

The molar mass of Cu is 63.55 g/mol.

0.070 mol × 63.55 g/mol = 4.4 g

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

answer: gold foil experiment - he shot alpha particles at a gold foil

explanation: