Answer:
Density, melting point. and magnetic properties
Explanation:
I can think of three ways.
1. Density
The density of Cu₂S is 5.6 g/cm³; that of CuS is 4.76 g/cm³.
It should be possible to distinguish these even with high school equipment.
2. Melting point
Cu₂S melts at 1130 °C (yellowish-red); CuS decomposes at 500 °C (faint red).
A Bunsen burner can easily reach these temperatures.
3. Magnetic properties
You can use a Gouy balance to measure the magnetic susceptibilities.
In Cu₂S the Cu⁺ ion has a d¹⁰ electron configuration, so all the electrons are paired and the solid is diamagnetic.
In CuS the Cu²⁺ ion has a d⁹ electron configuration, so all there is an unpaired electron and the solid is paramagnetic.
A sample of Cu₂S will be repelled by the magnetic field and show a decrease in weight.
A sample of CuS will be attracted by the magnetic field and show an increase in weight.
In the picture below, you can see the sample partially suspended between the poles of an electromagnet.
Salt dissolving into water is a physical change because it can be reversed as in chemical change cannot be reversed as in you can boil water and have the salt on the bottom
Answer:
0.098 moles H₂S
Explanation:
The reaction that takes place is
- 2H₂(g) + S₂(g) ⇄ 2H₂S(g) keq = 7.5
We can express the equilibrium constant as:
- keq = [H₂S]² / [S₂] [H₂]² = 7.5
With the volume we can <u>calculate the equilibrium concentration of H₂</u>:
- [H₂] = 0.072 mol / 2.0 L = 0.036 M
<em>The stoichiometric ratio</em> tells us that <u>the concentration of S₂ is half of the concentration of H₂</u>:
- [S₂] = [H₂] / 2 = 0.036 M / 2 = 0.018 M
Now we <u>can calculate [H₂S]</u>:
- 7.5 = [H₂S]² / (0.018*0.036²)
So 0.013 M is the concentration of H₂S <em>at equilibrium</em>.
- This would amount to (0.013 M * 2.0 L) 0.026 moles of H₂S
- The moles of H₂ at equilibrium are equal to the moles of H₂S that reacted.
Initial moles of H₂S - Moles of H₂S that reacted into H₂ = Moles of H₂S at equilibrium
Initial moles of H₂S - 0.072 mol = 0.026 mol
Initial moles of H₂S = 0.098 moles H₂S
