The most common way for electrons to move to an excited state is by absorption of electromagnetic radiation. When an electron absorbs this radiation, it takes in the energy that the wave contains and this causes it to move to a higher energy state. They come back to ground state at the first possible opportunity because in the excited state they have lots of potential energy. Electrons can make different jumps in energy levels when it loses this potential energy (ie. it can go directly to the ground state, or it can go to lower energy levels and then the ground state). When they move to lower energy levels, the electrons emit the electromagnetic radiation that was absorbed - the frequency of the waves emitted depends on the electron's jumps between energy levels as it returns to ground state.
Answer:
Carbon nanotubes have a very high melting point, as each carbon atom is joined to three other carbon atoms by strong covalent bonds. This also leaves each carbon atom with a spare electron, which forms a sea of delocalised electrons within the tube, meaning nanotubes can conduct electricity.
Explanation:
A) 5Ca(OH)₂ + 3H₃PO₄ → Ca₅(PO₄)₃(OH) + 9H₂O
B) m=158 g; w=0.830; m{Ca(OH)₂}=123 g
n(H₃PO₄) = m(H₃PO₄)/M(H₃PO₄) = mw/M(H₃PO₄)
n(H₃PO₄) = 158g*0.830/(98.0g/mol) = 1.3382 mol
n{Ca(OH)₂}=m{Ca(OH)₂}/M{Ca(OH)₂}
n{Ca(OH)₂}=123g/(74.01g/mol)=1.6619 mol
Ca(OH)₂:H₃PO₄ = 5:3
1.6619:1.3382 = 5:4 the limiting reagent is a calcium hydroxide
m{Ca₅(PO₄)₃(OH)} = M{Ca₅(PO₄)₃(OH)}n{Ca(OH)₂}/5
m{Ca₅(PO₄)₃(OH)} = 502.3g/mol*1.6619/5=166.954 g*
*The statement of the problem is incorrect, surplus of a phosphoric acid reacts with a hydroxyapatite. The calculated quantity of a hydroxyapatite is not formed.
3Ca₅(PO₄)₃OH + H₃PO₄ = 5Ca₃(PO₄)₂ + 3H₂O
