1 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e

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1 1 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e Chapter 7 The Mole: A measurement of matter Vocabulary: Mole (mol) Avogadro Number = 6.02 x 1023 Representative particle Gram atomic mass Gram molecular mass Gram formula weight (mass) gfw Empirical formula Percent composition Molecular formula Standard temperature and pressure (STP) Liter Molar volume Molar mass Ionic compound Covalent compound Hydrate Percent by mass Ratio Quantitative Reactants Products Chemical reactions Conversion factor Section 7-1 Chemistry is a science. In your study of chemistry you will analyze the of samples of matter. How do you measure matter? of particles,,. Units of matter used in Chemistry are the mole, L, g. How many apples are in a dozen apples? What is a mole? How are moles similar to dozens? When would you use a conversion factor?

2 2 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e Lab #1: Can you count by weighing? Purpose: Materials: Paper clips, a balance. Procedure: 1. Weigh one paper clip, record the mass in the data table. 2. Weigh 25 paper clips. Record the mass in the data table. 3. Calculate the average mass of one paper clip, by taking the mass of 25 paperclips and dividing by 25. Calculate the % deviance by subtracting your average mass mass of one paper clip. This is the deviance. To calculate the % deviance, divide the difference in masses by the mass of an average paperclip and multiply by Take a handful of paperclips. Measure the mass. 5. Predict the number of paperclips. 6. Evaluate your prediction, can you mass the paperclips in order to determine how many? Explain. Results: Step Description measurement 1. Mass of one paper clip 2. Mass of 25 paper clips 4. Mass of a handful of paper clips. 7. Count how many paper clips in the handful. Calculations: = Step 5: predict, how many paper clips Use the average mass of a paperclip as a conversion factor to calculate how many paper clips. Conclusions: Minimum five sentences. Section 7.1 continued. The number of particles in a MOLE

3 3 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e One way to measure the amount of a substance is to of particles in a substance. Because atoms, molecules, and ions are ridiculously small, the number of individual particles (even in a tiny sample) are. A mole (mol) of a substance = representative particles. The experimentally determined number is called the Number. The term representative particle refers to. Seven elements,,,,,,, normally exist as diatomic molecules. These are called either the magic 7 or the HONCLBrIF club. Representative particles of molecules are, for example CO 2 consists of one and 2 atoms in one molecule of CO 2. In H 2 O there are 2 and 1 per molecule. In C 6 H 12 O 6 there are 6 atoms each of and, and 12 atoms of in each molecule of glucose. In Sucrose, C 12 H 22 O 11 there are atoms of Carbon, atoms of Hydrogen and atoms of oxygen. For ionic compounds, the atoms are put together similarly, so CaO has one ion of and one ion of. In Ca 3 (PO 4 ) 2 the math is a little more complicated, but there are 3, 2 and 8. In Mn(C 2 H 3 O 2 ) 3 there are Mn, C, H, and O. How many moles are in 2.8 x 1024 atoms of silicon? ( )( )_ ( ) How many molecules are mol of water? ( )( )_ ( ) How many moles are in 6.02 x 1022 atoms of Fe? ( )( )_ ( ) How many moles are in 1.2 x 1023 molecules of H 2?

4 4 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e Simple mole practice: Given moles, find molecules moles Ca(OH) moles CH moles H x 10-2 moles C 6 H 12 O moles CO x 1010 moles C 18 H 36 O x moles HCl x moles Br 2 Given molecules, find moles molecules Mg(OH) molecules SiH molecules H x 102 molecules C 6 H 12 O molecules CS x 1010 molecules C 18 H 36 O x 1018 molecules HBr x 1020 molecules Br2 Did you notice that the number of molecules is always MUCH larger than the corresponding number of moles?

5 5 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e 1. How many atoms of chlorine are in 2.23 moles of Cl 2? 2. How many atoms of hydrogen are in 3.33 moles of C 6 H 12 O 6? 3. How many atoms of phosphorous are in 600 moles of H 3 PO 4? 4. How many atoms of oxygen are in 600 moles of phosphoric acid, H 3 PO 4? 5. In a sample of Cl 2 O 7 containing atoms of chlorine, how many moles of dichloro heptoxide are there? 6. In a sample of carbon dioxide containing 6.02 x molecules of oxygen, how many moles of carbon dioxide are there? 7. In a sample of dichloro pentoxide containing 6.02 x 1020 molecules of oxygen, how many moles of Cl 2 O 5 are there?

6 6 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e Lab #2 How many molecules and atoms are in your name. Background: Chalk is made either of calcium carbonate or calcium sulfate. As you write your name on paper, molecules from the chalk are deposited onto the paper. The chalk loses mass as the paper gains the mass. Calcium sulfate has a mass of 136 grams in every mole. Purpose: To relate the number of molecules and atoms to something about you. Procedure: 1. Find the mass of a piece of chalk. Record the mass in your data table. 2. Write your name on a piece of paper. 3. Find the new mass of the chalk. Record the mass in your data table. 4. Repeat steps 1 3 for each lab partner. Results: Student name Initial Mass of chalk Final mass of chalk Change in mass of chalk Calculations: 1. Calculate the number of moles in the chalk for each student. Change in mass (g) Divide 136 g/mole Moles of chalk 136 g/mole = 136 g/mole = 136 g/mole = 136 g/mole = 2. Calculate the number of molecules in the chalk for each student. Moles of chalk (mol) Multiply by Avagadro Number X 6.02x10 23 molecule 1 mole X 6.02x10 23 molecule 1 mole X 6.02x10 23 molecule 1 mole X 6.02x10 23 molecule 1 mole Molecules of chalk

7 7 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e 3. Calculate the number of atoms of calcium. Molecules of chalk Multiply by subscript for calcium in CaSO 4 Atoms of calcium 4. Calculate the number of atoms of sulfur. Molecules of chalk Multiply by subscript for sulfur in CaSO 4 Atoms of sulfur 5. Calculate the number of atoms of oxygen in CaSO 4 Molecules of chalk Multiply by subscript for oxygen in CaSO 4 Atoms of oxygen Conclusions: Discuss the size of a mole compared to the number of atoms in a mole. How is subscript related to the number of atoms? Are the number of moles much larger, or much smaller than the number of molecules and atoms? What are sources of uncertainty in this lab (what probably went wrong). Did longer names use more or less atoms and molecules than shorter names? Were there any other factors which influenced the number of molecules and atoms used? (minimum 5 sentences).

8 8 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e Section 7.1 The Mass of a Mole of an Element. 1. Why would one want to use moles rather than atoms to measure the mass of a substance? 2. List the gram atomic masses of the following elements: a) Fe b) O c) S d) K e) Pb f) C 3. If you were to compare 12.0 grams of carbon atoms with 16.0 grams of oxygen atoms, how are the number of atoms related? The Mass of a Mole in a Compound. 4. How many sulfur atoms are in sulfur trioxide? 5. How many oxygen atoms are in sulfur trioxide? 6. To find the mass of sulfur trioxide, what should you do? Find the following molecular masses (gram formula weight): CO 2 = ( ) + 2 ( ) = NaOH = ( )+ ( )+ ( )= Ca 3 (PO 4 ) 2 = 3 ( )+ 2 ( )+ 8 ( )= Ca(C 2 H 3 O 2 ) 2 = 1( )+ 4( )+6( )+4( ) MnPO 4 = CuSO 4 = (NH 4 ) 3 PO 4 = Ca(OH) 2 = H 2 O 2 = C 3 H 7 OH = N 2 O 5 = Carbon tetrabromide = Sodium phosphate Ammonium carbonate

9 9 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e Section 7.1 How are mass and moles related to the gram formula weight (molar mass) Find the moles of the following: grams N 2 O grams of (NH 4 ) 2 CO grams of C 2 H grams C 3 H 7 OH g CBr 4 How many grams of each are in the following number of moles? mole CH moles Cl moles NH 3

10 10 P a g e C h a p t e r 7 C h e m i c a l Q u a n t i t i e s a n d t h e M o l e