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

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.