<span>Not all solids melt when they are heated. Some may undergo chemical changes as a result of heating. For example paper burns rather than melts</span>
Answer:
En el caso del sodio, la valencia es 1, ya que tiene un solo electrón de valencia, si pierde un electrón se queda con el último nivel completo.
Explanation:
Grupo de la tabla periódica Electrones de valencia
Grupo 14 (IV) (Grupo del carbono) 4
Grupo 15 (V) (Grupo del nitrógeno ) 5
Answer:
Few important points related to 
reaction:
1. is a one-step reaction that follows second order kinetics.
2. In reaction, a transition state is formed in situ.
3. Strong nucleophiles like 
are used in case of bi-molecular nucleophilic substitution reaction.
Ethyl acetate can be prepared by a second-order nucleophilic substitution reaction between acetic acid and ethyl bromide.
The reaction between acetic acid and ethyl bromide is drawn below:
a) According to the reaction equation:
CaSO4(s) ↔ Ca2+(aq) + SO4-(aq)
when Kc = [Ca2+][SO4-]
when [Ca2+] = [SO4-] = X
and we have Kc = 2.4 x 10^-5 so ,by substitution we can get [Ca2+]&[SO4-]
2.4 x 10^-5 = X^2
∴X = 0.0049
∴[SO4-] = [Ca2+] = 0.0049 M
b) when we have [Ca2+] = 0.0049 M so we can get the no.of moles of CaSO4:
moles of CaSO4 = molarity * volume
= 0.0049 M * 1.2 L
= 0.00588 moles
when we know the molar mass of CaSO4 = 136.14 g/ mol, So we can get the mass:
∴mass of CaSO4 = moles of CaSO4 * molar mass of CaSO4
= 0.00588 moles * 136.14 g/mol
= 0.8 g
