On the first day I did a reaction between copper and nitric acid. In that demons

Question

On the first day I did a reaction between copper and nitric acid. In that demonstration I combined two pennies, minted before 1982, with some concentrated nitric acid. Recall that old pennies are 100% copper and have a mass of 3.1 g. What is the balanced equation for the reaction: Cu reacts with HNO_3 and NO_2 gas is one product? The other products are Cu(NO_3)_2 and H_2O. What volume of concentrated HNO_3 is needed to completely dissolve the pennies? Concentrated HNO_3 has a density of 1.42 g/mL. What is the molarity of this concentrated HNO_3? The reddish-brown gas that is produced is NO_2. Draw the Lewis Electron Dot picture for this molecule. What is the shape of the molecule and what hybridization is present in the molecule? If the reaction is carried out at room temperature, 25 degree C, and room pressure 1 atm, what volume of NO_2 gas is produced?

Explanation / Answer

C)

Molatiy = number of moles of solute/ litres of solution

Here we are only given the density of HNO3 = 1.42 g/mL

Let's First calculate the molecular mass of HNO3 :

H - 1, N - 14 , O - 16

1 + 14 + (3 x 16) = 68g

Density = mass / volume

Molatiy = number of moles of solute/ litres of solution

Molatiy = 1.42/68 x 10-3

Molatiy = 0.00002M

e) The equation can be balanced as follows :

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

Now we calculate the number of moles of Cu

n = 3.1/63.5

n = 0.049 (rounder to 3 decimal places)

From the eqn we see that 1 mole of Cu produces 2 moles of NO2, hence 0.049 moles of Cu will produce 2 x 0.049 moles of NO2.

Hence no . of moles of NO2 = 0.098

We know that :

PV = nRT

1 x V = 0.098 x R x 298K

calculating we get :

V = 2.429 Ltr

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