Stoichiometric Problem

[Lily Mohtashami]

In a stoichiometric problem if the masses of each reactant are not given can you assume that the mass is 100g like you can do when finding the empirical formula, and then can you use this 100g to convert masses to moles?

[Hannah Lechtzin 1K]

This only works for finding the empirical/molecular formula because you are finding out what proportion of a chemical each element makes up. When doing a stoichiometric problem you should be given some value like the amount of atoms, moles, or mass of a reactant that allows you to convert the given value into the value you are looking for. I hope this helps!

[rita_debbaneh2G]

You'll probably be given what you're looking for in the form of, say, atoms. You can use the equation N=nNa to calculate for whatever you need to find with N=atoms/molecules/etc of whatever, n= moles of whatever, and Na= Avogrado's constant.

[isha dis3d]

Hi bff so in the stoichiometric problem you would use the chemical equation to find ratios between any two molecules. From there you can use the ratio of moles to convert from moles to grams using molar mass.

[Sidharth Paparaju 3B]

No--because molecular equations use based off the stoichiometric coefficients (like how many moles you have), you need to convert to moles (since grams cant be used). For example, 1 gram of Hydrogen is more particles than 1 gram of Sodium. So, even though there is the same amount of weight, there isn't the same amount of particles present.

[emmakvarnell]

Assuming 100g should only be used when solving for the empirical formula. This method is used to reach the relative ratio between atoms in a molecule, not to reach the specific values of moles/grams that stoichiometric problems require. A stoichiometric problem should give you important values needed for the problem, or should have existing equations needed to solve for the problems.

[Chem_Mod]

Hello Lily,

As previously noted, assuming 100 g is relevant only for the empirical/molecular formulas.

In given a stoichiometric problem, if you asked an array of questions (e.g. how much product is formed, how much reactant is consumed, &c) an amount (such as g, mols, mmols, &c) will be provided to decipher other characteristics about the reaction.