Lanthamides, actinides, noble gases
Answer:
sodium carbonate decahydrate
Explanation:
Usually we would the molar mass of Na2CO3 x 10 H2O. This is where the name comes from.
Answer:
The enthalpy change for the reaction is ΔH = - 54.3 kJ/mol
Explanation:
The reaction between HCl and NaOH is a neutralization reaction:

Heat released during neutralization = Heat gained by water
i.e. 
where:

m = total mass of solution

ΔT = change in temperature = 22.8 - 21.5 = 1.3 C
c = specific heat = 4.18 J/g C

As per equation (1): qrxn = -434.7 J
The reaction enthalpy ΔH is the heat released per mole of acid (or base)


Answer:
number of valence electrons
Explanation:
All of the elements in group 17, also known as group 7A, have 7 valence electrons.
No two elements have the same atomic number nor atomic mass in elemental form.
Halogens may have any number of isotopes.
The temperature at which a liquid turns into a solid when cooled