Answer: The volume of nitrogen evolved at STP when 63 g of ammonium dichromate is heated is approximately 5.6 L.
Step-by-step explanation:
To find the volume of nitrogen evolved, we'll first need to determine the moles of ammonium dichromate used, and then use the stoichiometry of the balanced equation to find the moles of nitrogen produced. Finally, we'll convert the moles of nitrogen to volume at STP.
The balanced equation is:
(NH4)2Cr2O7 -> Cr2O3 + 4H2O + N2
Calculate the molar mass of ammonium dichromate, (NH4)2Cr2O7:
2 * (14.01 [N] + 4 * 1.01 [H]) + 2 * 51.99 [Cr] + 7 * 16.00 [O] =
2 * (14.01 + 4.04) + 103.98 + 112.00 = 252.06 g/mol
Calculate the moles of ammonium dichromate:
63 g / 252.06 g/mol ≈ 0.25 mol
Use stoichiometry to find moles of nitrogen produced:
1 mol (NH4)2Cr2O7 produces 1 mol N2, so 0.25 mol (NH4)2Cr2O7 produces 0.25 mol N2.
Convert moles of nitrogen to volume at STP (standard temperature and pressure):
At STP (0°C and 1 atm), 1 mole of any gas occupies 22.4 L. Therefore, 0.25 mol N2 occupies:
0.25 mol × 22.4 L/mol ≈ 5.6 L
So, the volume of nitrogen evolved at STP when 63 g of ammonium dichromate is heated is approximately 5.6 L.