Unit 4 ~ Learning Guide Name:

Transcription

1 Unit 4 ~ Learning Guide Name: Instructions: Using a pencil, complete the following notes as you work through the related lessons. Show ALL work as is eplained in the lessons. You are required to have this package completed BEFORE you write your unit test. Do your best and ask questions if you don t understand anything! The Mole: 1. What is the definition of a mole? Note that you may also see this term written as mol. 2. What is the value of a mole? 3. How would you enter this number into your calculator? Avogadro's Number: 1. Fill in the symbols for the following terms Term Symbol Avagadro's Number mole Number of Particles Page 1 of 15

2 Mole Calculations: Show your work for all of these questions. Remember to ensure units cancel properly while doing unit conversions. Hint: If you are ever getting an answer with powers in the 40s then you have a unit conversion upside down! There are hints for these in the answer key but you should try them on your own first! This will be true for the rest of the sections in this learning guide as well. 1. How many grams are there in 2.3 moles of sulfur? 2. How many grams are there in 5.15 moles of mercury? 3. How many moles are there in 47 grams of iron? 4. How many moles are there in 215 grams of copper? 5. How many atoms are there in 5.2 moles of zinc? 6. How many atoms are there in 31.6 moles of magnesium? 7. How many moles are there in atoms of enon? 8. How many moles are there in atoms of potassium? Page 2 of 15

3 9. How many atoms are there in 37.5g of aluminum? 10. How many grams are there in atoms of manganese? Molar Mass and Compounds: 1. Determine the molar mass of the following compounds. Show your work in the bo provided. Remember to provide the correct units in your final answer. Formula Work Molar Mass FeS Ni 2 O 3 C 12 H 22 O 11 (NH 4 ) 3 PO 4 Mn(MnO 4 ) 4 2. What do we use to convert between grams and moles? Page 3 of 15

4 3. Particles is one of the overall term for atoms and molecules. You may also see the term formula units used when dealing with ionic compounds. What do we use to convert between moles and particles? 4. How many molecules of MgCl 2 are in 205 g of MgCl 2? 5. How many atoms of hydrogen are there in 25.3g of CH 4. Note this will require THREE unit conversions to answer correctly! 6. How many oygen atoms are there in 98.4g of oygen gas. Hint: oygen gas just might be diatomic! Be warned that on a test you will NOT be told if an element is diatomic. You need to memorize the diatomic elements. 7. If a sample of Fe 2 S 3 contains iron atoms what is the mass in grams? Page 4 of 15

5 Characteristics & Molar Volume of Gases: 1. What does STP stand for? 2. What is the main difference between STP and SATP? Please don't say the A! 3. What is the molar volume at STP and SATP? Be sure to include the correct units. Note that these values are on your data table so you do NOT need to memorize them. 4. What volume in litres does 27.3 g of argon gas occupy at STP? 5. What volume in litres does 85.4 g of nitrogen gas occupy at SATP? 6. How many moles of bromine gas are there in a volume of 80.0L at STP? 7. How many atoms of hydrogen are there in 129 L of ethane gas (C 2 H 6 ) at SATP? Page 5 of 15

6 Percent Composition: 1. What is the definition of percent composition? 2. What is the percent composition of each element in SiCl 4? 3. What is the percent composition of each element in Ca(BrO 3 ) 2? Page 6 of 15

7 Empirical Formula: 1. What are the 3 steps to determining an empirical formula given the percent composition of compound? 2. A compound is found by analysis to be by mass 79.85% carbon and 20.15% hydrogen. What is its empirical formula? 3. A compound is found by analysis to be by mass 24.4% calcium, 17.1% nitrogen and 58.5% oygen. What is its empirical formula? Page 7 of 15

8 4. The empirical formula of a substance indicates the simplest whole number ratios of the different kinds of atoms that make up the substance. The empirical formula of a substance with the molecular formula N 2 O 4, for eample. is NO 2. Fill in the table with the empirical formula for each of the following hydrocarbon compounds. Compound Name Molecular Formula Empirical Formula methane CH 4 benzene C 6 H 6 ethane C 2 H 6 ethylene (ethane) C 2 H 4 octane C 8 H 18 acetylene (ethyne) C 2 H 2 Naphthalene C 10 H 8 5. After substantial heating, 0.476g of uranium produced g of a compound with oygen. Determine the empirical formula. Hint: you will need to subtract those 2 numbers to get a mass of oygen to work with. Page 8 of 15

9 Molecular Formula: 1. What is the difference between a molecular formula and an empirical formula? 2. The empirical formula of a compound is CH 3. Its molar mass is g/mole. What is its molecular formula? 3. A compound has the following percentage mass composition: 71.35% carbon, 12.00% hydrogen, and 16.65% nitrogen. Its molar mass is g/mole. Determine its molecular formula. Page 9 of 15

10 Molar Concentration (Molarity): 1. What is the difference between a solute and a solvent? 2. If 33.7 moles of MgCl 2 is dissolved to make 8.3L of solution, what is the molarity of the solution? 3. If 275.2g of KMnO 4 is dissolved in to make L of solution, what is the molar concentration of the solution? L of carbon dioide gas at STP is compressed and then dissolved in 10.0 L of water. What is the molar concentration of the resulting solution? Page 10 of 15

11 Solutions and Dilutions: 1. Why is a volumetric flask much better than a beaker for preparing solutions with accurate known concentrations? 2. If [K 3 PO 4 ] M, how many grams of K 3 PO 4 are in ml of solution? Remember that M is the same as mol/l. 3. What volume in ml of M aluminum sulfate solution can be prepared using grams of aluminum sulfate? Hint: Remember you need to balance aluminum and sulfate to create the correct chemical formula Page 11 of 15

12 4. What is the resulting concentration of BaBr 2(aq) when 400. ml of water are added to 375. ml of M BaBr 2 (aq)? 5. How much water needs to be added to 15.0 ml of a concentrated solution of HCl (aq) to lower it's concentration to 1.00 M? Note that you can look up the concentration of concentrated HCl (aq) on your data table. Answers: Mole Calculations Hints: This is the layout you need to solve these questions. Notice that the units always cancel! ( ) 1. mol S 2. mol Hg ( 0( *+, ) *+, 0( 3. g Fe *+, 34 ( g Cu *+, 78 ( mol Zn ;<+* >? *+, >? 6. mol Mg ;<+* A( *+, A( 7. atoms Xe 9. g Al *+, J, ( J, *+, F4 ;<+* F4 ;<+* J, K *+, J, 8. atoms K *+, F4 ;<+* H 10. atoms Mn *+, A? ( A? ;<+* A? *+, A? Page 12 of 15

13 Mole Calculations Answers: g S g S or g Hg mol Fe mol Cu atoms Zn atoms Mg mol Zn mol K atoms Al g Mn Molar Mass and Compounds Hints: This is the layout you need to solve these questions. Notice that the units always cancel! 4. g MgCl L *+, A(7, M ( A(7, M *+,4N8,4 A(7, M *+, A(7, M 5. CH O *+, 70 P 6. g O L *+, R M *+,4N8,4 70 P 70 P *+, 70 P *+,4N8,4 R M ( R M *+, R M 7. atoms Fe *+,4N8,4 34 M) S ;<+* 34 ;<+* 0 *+,4N8,4 70 P ;<+* R *+,4N8,4 R M *+, 34 M ) S ( 34 M ) S *+,4N8,4 34 M ) S *+, 34 M ) S Molar Mass and Compounds Answers: g/mol, g/mol, g/mol, g/mol, g/mol molecules MgCl atoms H atoms O g Fe 2 S 3 Characteristics & Molar Volume of Gases Hints: This is the layout you need to solve these questions. Notice that the units always cancel! 4. Ar *+, JU ( JU V JU *+, JU 5. *+, W M ( W M V W M *+, W M 6. Br L *+, YU M V YU M 7. C L H Z *+, 7 M0 [ *+,4N8,4 7 M0 [ 7 M 0 [ *+, 7 M 0 [ ;<+* 0 *+,4N8,4 7 M 0 [ Page 13 of 15

14 Characteristics & Molar Volume of Gases Answers: L Ar L N mol Br atoms H Percent Composition Hints: First step for all of these questions is to calculate the molar mass of the compound! Percent Composition Answers: 2. %Si 16.53% %Cl 83.47% 3. %Ca 13.55% %Br 54.01% %O 32.45% Empirical Formula Hints: This is the layout you need to solve these questions. Notice that the units always cancel! 2. g C *+, 7 ( 7 and g H *+, 0 ( 0 3. g Ca *+, 7; ( 7; and g N *+, W ( W and g O *+, R ( R 5. g U *+, ( _ and g O *+, R ( R Empirical Formula Answers: 2. CH 3 3. CaN 2 O 6 5. U 2 O 3 Molecular Formula Hints: This is the layout you need to solve these questions. Notice that the units always cancel! 3. g C *+, 7 ( 7 and g H *+, 0 ( 0 and g N *+, W ( W Molecular Formula Answers: 2. C 2 H 6 3. C 15 H 30 N 3 Page 14 of 15

15 Molar Concentration Hints: 3. First calculate the mols using this layout: g KMNO O *+, HAWa P ( HAWa P 4. First calculate the mols using this layout: L CO L *+, 7R M V 7R M Molar Concentration Answers: 2. [MgCl 2 ] 4.1 M 3. [KMnO 4 ] 3.48 M 4. [CO 2 ] M Solutions and Dilutions Hints: 2. ml K c PO O V H S er P *V H S er P *+, H SeR P V H S er P ( H S er P *+, H S er P 3. g Al L (SO O ) c *+, J, M()R P ) S V J, M ()R P ) S ( J, M ()R P ) S *+, J, M ()R P ) S *V J, M()R P ) S V J, M ()R P ) S 4 and 5. Remember that: [Final] Final Volume [Initial] Initial Volume Solutions and Dilutions Answers: g K 3 PO ml Al 2 (SO4) 3 4. [Final] M M 5. Water added 159 ml Page 15 of 15