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chem help asap!!! STOICH and limiting reactanct!!! Please help me I'm so confused!!?
please help me answer and show work!!
Cu + 4HNO3= Cu(NO3)2 +2NO2 +2H2O
You have 9.35 g Cu and .4 mol of HNO3
1. how many mol of Cu were initially dropped in the nitric acid?
2. One of these reactants were in excess, which and how did you know? (show the ratio)
3. What mass of Cu reacted?
4. What mass of Cu remained after the reaction was over
5. WHat volume of gas measured at STP escaped during the reaction?
6. what is the name of the blue crystalline substance left behind after the evaporation of the water?
7. WHat should be the mass of this blu crystalline substance? (formed after the reaction is completed, removing the unreacting copper and heating the remaining liquid to evaporate the water and form it)?
Ill give best answer and 5 stars please!!
Assuming all the copper was put in the solution, moles that were added were:
9.35g/63.54g/mole = 0.147mole
To determine excess reactant, you need to know moles of all reactants and balanced equation:
There are 0.147mole of copper and:
0.4 mole of HNO3, but from the balanced equation you can see that you need 4 HNO3's for each Cu (which would require 4 x 0.147 moles, so we can see that there is not enough HNO3 to react all of the copper.
The mass of copper that reacted is the moles of HNO3, divided by 4, multiplied by the weight for copper per mole:
(0.4mole/4) x 63.54g/mole = 6.354g
The mass of Cu left over is:
(9.35 - 6.354)g = 2.996g ~ 3g
The volume of gas can be determined from the moles of copper reacted and the ratio from the balanced reaction:
0.1mole copper reacted x 2 mole NO2/moleCu = 0.2 mole of NO2
A mole of any gas at STP occupies 22.4 liters
So: volume of gas will be 0.2mole x 22.4l/mole = 4.48 liter
The blue crystalline substance is called copper (II) nitrate or cupric nitrate.
The mass of cupric nitrate can be determined from the moles of copper reacted and the molecular weight for the material. (The ratio from the balanced equation for Cu reacted to Cu(NO3)2 produced is 1 to 1:
Molecular weight of Cu(NO3)2 is:
63.54 + (2 x 14) + (6 x 16) = 187.54g/mol
(6.354gCu/63.54) x 187.54 = 18.754g
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