Hello!
The number of 20-g ice cubes required to absorb 47 kJ from a glass of water upon melting is 7 icecubes
Why?
We are going to clear from the equation of the released heat, the mass of ice (m). The specific latent heat of fusion of ice is 336 kJ/kg:

So, 7 ice cubes are required to absorb that amount of heat from the glass of water.
Have a nice day!
A sodium chloride is like most of the ionic compounds
existing here on earth in which they are composed of having a high melting
point and by this, if found in underground rock deposits, they are usually in a
form of solid.
Answer:
A. CsBr(s)
Explanation:
we will get here compound with the lowest lattice energy
solution
As we know that Lattice energy is always proportional to the charge of ions and it is inversely proportional to the size of ions.
so that by the smallest charge and the largest size give us the lowest lattice energy and that charge and size is express as here as
Charge
Cs (+1), K(+1), Na (+1), Cl(-1), Br(-1), Sr(+2), Ca(+2), O(-2) .......................1
and
Size
Na+ < Ca2+ < K+ < Sr2+ < Cs+, O2- < Cl- < Br- ..........................2
so that here
correct answer is A. CsBr