# Quantitive chemisrty

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## calculating mass of a number of molecules

First you need to know the chemical equation. Now you can figure out the relative atomic mass and this is easy: Take the chemical equation and find the atomic mass, if there are 2 or more you will have to times the mass by amount of molecules. Then you times it by the number of moles and then you have the mass.

Mass(g)=number of moles x relative atomic mass

This is a brilliant way to figure out how much the atom weighs, and how they make something weigh.

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## solutions

The more solute a solution is in a given volume, the more concentrated the solution is.

One way to measure the concentration is by calculating the mass of a substance in a given volume of solution.

Here's how to calculate the concentration:

concentration= mass of a solute

Volume of solvent

you can calculate the mass by switching the formula to: mass= concentration x volume

This formula is in G/dm3

For mol/dm3 it is:

concentration= number of moles of solute

volume of solvent

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## percentage yield

The amount of product you get is known as the yield. The more reactants you start with, the higher the actual yield will be- that's so obious!! The perecntage yield does not depend on the amount of reactants, because its a percentage.

This can be shown by a formula

Percentage yield= mass of product actually made          x 100

maximum theoreticl mass of product

You can rearrange the equation to figure out the mass of the product you made.

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## Number of moles

moles are a name given to an amount of a substance. Moles are just a number that we use to make it easier to see how many atoms there are in a substance. You can figure out this number by Dividing the mass by the Mr.

Number of moles= mass in g(of an element or compound)

Mr ( of the element or compound)

We already know mass and this is very similar to it, in fact you can rearrange the equation to show the mass. Go back to the first one to see the equation.

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