The solubility of a compound with a molecular weight of 226.9 is determined to be 22.1 g in 125.0 g of water at 398 K. Express this concentration in terms of molality.

The correct answer is 0.78 m

Explanation:

Molality is defined as moles of solute per kilogram of solvent and it is expressed as mol/kg. In this case, the solute is the compound (with a molecular weight of 226.9) and the solvent is water.

First, we calculate the number of moles of compound we have in solution. For this, we divide the mass of compound into the molecular weight:

moles solute = 22.1 g x 1 mol/226.9 g= 0.097 mol

We have 0.097 moles of compound in 250 g of solvent (water) and we want to know the moles in 1000 g (1000 g= 1 kg):

0.097 mol x 1000 g/250g= 0.779 mol/kg = 0.078 m

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

i think   the answer is c hope i'm right