How much Pb(NO3)2 would need to be added to 100 mL of water to make a saturated solution at 40°C.

70g of Pb(NO3)2 would need to be added

Explanation:

As you can see in the solubility graph of lead nitrate, Pb(NO₃)₂, the solubility of this salt (That is, the maximum amount of the salt that can be dissolved in 100g of the solvent producing a homogeneous solution) is 70g in 100g of water = 70g of the salt in 100mL of water.

A saturated solution is also defined as solubility: The maximum amount of a solute that can be dissolved in a solvent.

That means:

70g of Pb(NO3)2 would need to be added

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.