Not understanding on how stoichiometry works not sure which side to start on. ex: How many grams of water are required to form 75.9 g of HNO3? Assume that there is excess NO2 present. The molar masses are as follows: H2O = 18.02 g/mol, HNO3 = 63.02 g/mol.

3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)

Explanation:

We will need a chemical equation with masses and molar masses, so, let's gather all the information in one place.

Mᵣ:                            18.02           63.02

              3NO₂(g) + H₂O(ℓ) ⟶ 2HNO₃(aq) + NO(g)

m/g:                                               75.9

You start with the substance for which they give you numbers.

For example, this question gives you the mass of HNO₃ and asks you to find the mass of water.

You start with the mass of HNO₃.

Then you convert mass of HNO₃ ⟶ moles of HNO₃ ⟶ moles of water ⟶ mass of water

(a) Moles of HNO₃

(b) Moles of H₂O

(c) Mass of H₂O

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.