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Mole concept Introduction

Mole concept Introduction

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- 1. TOPIC-1 QUANTITATIV E CHEMISTRY
- 2. Measurementand Units A lot of experimental chemistry relies on accurate measurement which should allow the scientific community to communicate effectively across the disciplines and border. Scientist have developed the SI system SystemeInternational
- 3. SI UNITS Mass _ kg 1000 g = 1 kg 1000 mg = 1 g Time – s 60 sec = 1 min 60 min = 1 hr Temperature – K Based on thermal motion Absolute zero (all thermal motion ceases) K = ˚C + 273
- 4. Volume –m3 (cubic metre) 1 L = 1 dm3= 1000 mL Pressure –Pa (Pascal) 1 atmosphere = 1.01 x 105Pa = 101 kPa thesequantitiesarehowevernotalwaysconvenientforthe quantitiestypicallyusedinlaboratory In a lab: Mass in g volume in cubic centimetre Pressure in atm.
- 5. Amounts of Substances Chemist need to measure quantities for certain purposes. As we know that, all matter composed of varying types of substances which are Atoms–building blocks of matter; extremely small; exist as varieties in universe (elements) Compounds–substances composed of atoms joined together in whole-number ratios Because of size, atoms and compounds cannot be counted directly Counted based on mass and using mole concept
- 6. THE MOLE WHAT IS A MOLE ? it is the standard unit of amount of a substance - it is just a number, a very big number it is a way of saying a number in words, just like... DOZEN for 12 SCORE for 20 GROSS for 144 HOW BIG IS IT ? 602200000000000000000000 (Approximately)... THAT’S BIG !!! It is a lot easier to write it as... 6.022 x 1023 It doesn’t matter what the number is as long as everybody sticks to the same value
- 7. Avogadro No. or MOLE The ratios with which elements combine depend on the number of atoms not on their mass. Individual atoms and molecules are extremely small. Hence a larger unit is appropriate for measuring quantities of matter. A mole is the amount of substance which contains the same no. of chemical sps as there are atoms in exactly 12 g of the C-12 . Its S.I. unit is mol. This number is known as Avogadro’s constant. 1 mole is equal to 6.02 x 1023 particles. One gram of H atoms contains 6.02 x 1023 atoms.
- 8. THE MOLE WHY USE IT ? Atoms and molecules don’t weigh much so it is easier to count large numbers of them. In fact it is easier to weigh substances. Using moles tells you... how many particles you get in a certain mass the mass of a certain number of particles DO I NEED TO KNOW ANYTHING ELSE ? Yes, it would help if you can balance equations AND Keep trying, you will get the idea ... EVENTUALLY!
- 9. THE MOLE CALCULATING THE NUMBER OF MOLES OF A SINGLE SUBSTANCE moles = mass/ molar mass mass = moles x molar mass molar mass = mass / moles UNITS mass g or kg molar mass g mol-1 or kg mol-1 MOLES(n) = MASS(m) MOLAR MASS MASS __________ MOLES x MOLAR MASS
- 10. Molar Mass The mass of 1 mole of a species is c/d the molar mass. It is the relative mass expressed in g and has unit g/mol. The relative molecular mass(Mr) is defined as the sum of the relative atomic masses of the atoms in the molecular formula.it is expressed in g. Q-Calculatethe relative molecular mass ofethanol C2H5OH The relative molecular mass of the molecule ={relative atomic mass* no. of atoms}C,H,O = ( 2×12)+(6×1.01)+16.00 = 46.08
- 11. The term Relative molecular mass is used in case of molecules ,but in case of ions relative formula mass is used. Calculatetheno. ofmoles in4.00gof sodium hydroxide,NaOH. Sol:Relative atomic masses are Na=22.99,O=16,H=1.01 Relative formula mass =2.99+16.00+1.01 =40.00g/mol No. of moles(n)= m =4.00 =0.100mol M 40.00
- 12. MOLES OF A SINGLE SUBSTANCE 1. Calculate the number of moles of oxygen molecules in 4g oxygen molecules have the formula O2 relative mass will be 2 x 16 = 32 ; molar mass will be 32g mol-1 moles = mass = 4g = 0.125 mol molar mass 32g mol -1 2.What is the mass of 0.25 mol of Na2CO3 ? Relative Molecular Mass of Na2CO3 = (2x23) + 12 + (3x16) = 106 Molar mass of Na2CO = 106g mol-1 mass = moles x molar mass = 0.25 x 106 = 26.5g
- 13. Counting Particles Mass of an individual atom is measured by using Mass Spectrometer. From it: mass of 1 mole of12 C = 1.99252 x10-23 No. of atoms in one mole (12 g of12 C ) = 12 1.99252×10-23 = 602000000000000000000000 This is a big no. and is c/d Avogadro’s no. No. of Particles(N)= n x Avogadro's constant(L) N =n x L
- 14. Calculate the amount of water,H2O that contains 1.80 x 1024. N=n x L = 1.80 x 1024 =2.99 mol 6.02x1023 (the answer should be given to 3 significant figure- the same precision as the data given in the question. If the amount given was1.8x 1024 the correct answer would be 3.0
- 15. Calculate how many hydrogen atoms are present in 3.0 moles of ethanol( C2H5OH). n= In 1 molecule of ethanol there are 6 H atoms In 1 mole of ethanol ther are 6 moles of H atoms In 3 moles of ethanol there are 6×3 =18 moles of H atoms N = nL N =18 ×6.023×1023 = 1.08×1025
- 16. REACTING MASS CALCULATIONS CaCO3 + 2HCl ———> CaCl2 + CO2 + H2O 1. What is the relative formula mass of CaCO3? 40 + 12 + (3 x 16) = 100 2. What is the mass of 1 mole of CaCO3 100 g 3. How many moles of HCl react with 1 mole of CaCO3? 2 moles 4. What is the relative formula mass of HCl? 35.5 + 1 = 36.5 5. What is the mass of 1 mole of HCl? 36.5 g 6. What mass of HCl will react with 1 mole of CaCO3 ? 2 x 36.5g = 73g 7. What mass of CO2 is produced ? moles of CO2 = moles of CaCO3 moles of CO2 = 0.001 moles mass of CO2 = 0.001 x 44 = 0.044g

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