Answer: a disturbance that transfers energy.
Explanation:
Answer:
Over ninety percent of all the atoms in the Universe are hydrogen atoms.
Explanation:
Over ninety percent of all the atoms in the Universe are hydrogen atoms. By mass, hydrogen makes up about 75% of all matter in the Universe. Hydrogen atoms are also the smallest and lightest of all the atoms with only one electron and one proton in a common single hydrogen atom (called protium).
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.
3 moles FeCl2
Explanation:
For any chemical reaction, the balanced chemical equation tells you the ratio that must always exist between the reactants.
In your case, you have
FeCl2(aq) + 2NaOH(aq) → Fe(OH)2(s) ↓ + 2 NaCl(aq)
The stoichiometric coefficients that belong to iron(II) chloride and to sodium hydroxide, respectively, tell you the mole ratio that must exist between the two reactants when this reaction takes place.
Notice that you have a 1:2 mole ratio between the two reactants, so you can say that the reaction will always consume twice as many moles of sodium hydroxide than moles of iron(II) chloride.
Now, you know that 6 moles of iron(II) chloride are added to 6 moles of sodium hydroxide.
Use the aforementioned mole ratio to determine how many moles of iron(II) chloride will react with the moles of sodium hydroxide
6 moles NaOH ⋅ 1 mole FeCl2
———————
2 moles NaOH
= 3 moles FeCl 2
This tells you that in order for all the moles of sodium hydroxide to react, you need 3 moles of iron(II) chloride. The other 3 moles will not take part in the reaction, i.e. they are in excess.
So, you can say that
3 moles of FeCl 2 → will react
3 moles of FeCl 2 → will not react
Notice that sodium hydroxide is completely consumed before all the moles of iron(II) chloride get the chance to take part in the reaction.
This tells you that sodium hydroxide acts as a limiting reagent, i.e. it limits the amount of iron(II) chloride that takes part in the reaction from 6 moles to 3 moles.
Answer:
The reaction (E) 2 H₂O₂ (l) → O₂ g) + 2 H₂O (l) has a single species that is both oxidized and reduced.
Explanation:
Given the reaction (E):
2 H₂O₂ (l) → O₂ g) + 2 H₂O (l)
In hydrogen peroxide, oxygen has an oxidation state of -1. We can see that the reaction is balanced.
The products of the reaction are:
O₂ (the oxidation state of the Oxygen is 0)
H₂O (the oxidation state of the Oxygen is -2)
Hence, 1 mol of Oxygen changes its oxidation state from -1 to 0 (oxidation) and 1 mol of Oxygen changes its oxidation state from -1 to -2 (reduction).
The reaction (E) has a single species that is both oxidized and reduced.
