how do you calculate theoretical yield of something? I don't know where to find the formula

You go to the balanced chemical equation, and look at the mole ratio between the reactants and products.

The theoretical yield is the value calculated from stoichiometry of a reaction. For example, in the reaction
2H2 + O2 ==> 2H2O, we might ask what the theoretical yield of H2O is if we start with 2 grams H2.
2 grams H2 = g/molar mass = 2/2 = 1 mol.

2 mols H2 will produce 2 mols H2O and we know that by looking at the equation. Therefore, 1 mol H2 will form 1 mol H2O. Then, 1 mol (2 grams) is the theoretical yield for water if we start with 2 grams H2. Usually, when we talk about theoretical yield, we also talk about percent yield.
%yield = [actual yield)/theoretical yield] x 100.

In the above problem, suppose we said that we performed the experiment and we obtained 1.8 grams of water. Then the percent yield would be
%yield water = (1.8/2.0)x 100 = 90%.

I hope this helps.

To calculate the theoretical yield of a substance, you need a balanced chemical equation for the reaction you're interested in. Here are the steps to calculate theoretical yield:

1. Write a balanced chemical equation for the reaction.
2. Determine the molar ratio between the reactants and the product you want to calculate the yield for. This can be found by examining the coefficients in the balanced equation.
3. Convert the given mass or moles of the starting material (reactant) to moles using its molar mass.
4. Use the molar ratio from step 2 to calculate the moles of the desired product.
5. Convert the moles of the product to the desired units, such as mass, using its molar mass.

Let's consider an example reaction:

2H2 + O2 --> 2H2O

If you have 2 grams of H2 and you want to calculate the theoretical yield of H2O, you can follow these steps:

1. The balanced equation tells us that 2 moles of H2 will produce 2 moles of H2O.
2. Convert the given mass of H2 to moles using its molar mass. H2 has a molar mass of approximately 2 g/mol (2 H atoms * 1 g/mol each).
2 grams H2 = 2 g / (2 g/mol) = 1 mol H2
3. Since 2 moles of H2 produce 2 moles of H2O, the moles of H2O produced will also be 1 mole.
4. The molar mass of H2O is approximately 18 g/mol (2 H atoms * 1 g/mol + 1 O atom * 16 g/mol).
5. Finally, convert the moles of H2O to mass.
1 mol H2O = 18 g/mol * 1 mol = 18 grams.

Therefore, the theoretical yield of H2O, starting with 2 grams of H2, is 18 grams of H2O.

Remember, the theoretical yield represents the maximum amount of product that can be obtained assuming complete reaction and no losses. The actual yield may be lower due to various factors such as incomplete reactions, side reactions, or product losses during isolation.