# Masses and Moles

How do I work out Masses and Moles.

Answers
Hello,there are several equations for moles and mass. It depends what measurements you already have and what type of exercise it is. Usually you know the volume or concentration, molar mass you can find from the periodic table. There are three basic but most useful equations: mass=moles x molecular mass; moles= concentration x volume; moles= molecules x Avogadro's number.
Kotryna S.
06 March 2014
Mole is the amount of substance. While mass is of course that substance measured in terms of gram.
israr.tutor
12 March 2014
If you would like a lesson on all the moles equations, I would be happy to help
Nina K.
15 March 2014
The mass of one mole of a substance is equal to it's mass number (or the sum of mass numbers of the constituent particles in a molecule). Therefore you can work out how many moles in a given mass of substance like this:No of moles = mass of substance/(mass number of substance)you can rearrange to work out the mass like this:mass (in grams) = no of moles x mass number of substanceSo for example one mole of carbon weighs 12g. The mass number of CO2 = 2x16 + 12 =44 so one mole of C02 has a mass of 44g. Two moles of CO2 weighs 2 x 44 = 88g.The number of moles in 22g of CO2 = 22/44 = 0.5.One mole always contains the same number of particles which is given by avagadro's number.
mathmom
22 March 2014
Hi, if you need an easy-to-understand and short crash-course in this subject let me know :)
Usman O.
24 March 2014
Moles of compound or element  =  mass of compound or element / molar mass of compound or element
sai
06 June 2014
Mass is a basic quantity that measures amount of material whereas moles are relative quantity.We use moles mainly in reaction calculations. Lets suppose we take an example of Hydrogen and Oxygen reaction to produce water. 2H2 + O2                                                           2H2OIn this reaction 2 moles of Hydrogen reacts with 1 mole of Oxygen to produce two moles of water. For conversion between moles and masses we need to know atomic mass of elements.
tanveer
06 June 2014
The mass of a molecule is determined from the periodic table.  Adding up the atomic masses of the molecule gives its relative molecular mass (rmm). E.g. CO2 Has one carbon, (rmm 12) and two oxygen (rmm 16)So its rmm is 12 + (16*2) = 44The number of moles of a compound are worked out by the following equation.  Moles = mass of compound/ rmmSo in 10g of carbon dioxide you get10/44 = 0.23
stevec
16 June 2014
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Adam R.
13 July 2014
Moles = mass (g) divided by the Mr
.
27 July 2014
go through all the formulas and  then try to apply them accordingly
gupta.rashi
04 August 2014
Hello there Mass is always in grams.Molar mass is always in grams per mole.And moles is always in moles.Now if you take the mass of a substance and divide it by molar mass, you get moles. If you divide mass by moles, you get molar mass.Now if you multiply molar mass and moles together, you get mass.If you need anymore info contact me.
zakia
05 August 2014
Once you get a hang of the basic formulas.. answering the questions is a piece of cake once you practice alot.
zakia
05 August 2014
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rachaellee
05 August 2014
As some others have mentioned, a useful way to remember is the phrase "Gee, Mr Mole!" In this phrase Gee = mass(grams), Mr = the molar mass and Mole = number of moles. If you write this out as a triangle so that Gee (mass) is at the top and Mr & Mole is at the bottom. If you are calculating:Mass you would do Mr X MoleMolar mass (Mr) = Mass(g)/Moles Moles = Mass(g)/MrMake sure when you are doing this that you are always using the correct units for mass, lots of questions will give you Kg etc so its important to know how to convert these.
rachaellee
05 August 2014
Hello SararooAs you know all matter is made of atoms.Carbon 12 is a specific form of carbon. The atoms of carbon 12  contain 6 protons, six neutrons and six electrons.The atomic mass of Carbon 12 is therefore given as 12 (6 protons plus 6 neutrons. For our purposes electron are considered not to have mass)The amount of substance (atoms) contained in 12 grammes of carbon 12 is called a mole.This number is actually about 6 x 10^23 (an incredibly large number - officially called Avogadro’s constant). This is the exact number of atoms contained in 12 grammes of Carbon 12.So one mole of oxygen atoms also contains 6x10^23 oxygen atoms. However 1 mole of oxygen atoms does not have the same mass as 1 mole of carbon 12 atoms. This is because 1 atom of oxygen has a greater mass than one atom of Carbon 12.The ‘relative’ atomic mass number of oxygen is 16 (8 protons plus 8 neutrons). This means 1 mole of oxygen atoms (6x10^23 oxygen atoms) has a mass of 16 grammes. (The relative atomic mass is the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12. Hydrogen therefore has a relative atomic mass of 1 )Oxygen the gas (a MOLECULE)  is 02 ie 2 oxygen atoms together. So 1 mole of oxygen O2 MOLECULES contains 6x10^23 MOLECULES. Important note! MOLECULES not atoms - a molecule of Oxygen is 2 oxygen atoms combined. So the mass of a mole of oxygen gas (molecules) is 2 x 16 grammes = 32 grammes.Let’s do another example CO2This molecule contains 1 carbon atom and 2 oxygen atoms.1 mole of of carbon atoms is 12 grammes. 1 mole of oxygen atoms is 16 grammes. But we have 2 oxygen atoms. So 1 mole of CO2 is:C (12 grammes) + O2(16 grammes x2) = 44 grammesThis mole of CO2 also contains 6x10^23 of CO2 MOLECULES
John I.
11 August 2014