3 Chemical Formulas. AP Chemistry. Period Date / / STUDY LIST. I can: Formulas. Percent Composition

Transcription

1 3 Chemical Formulas I can: Formulas Look at a formula and state how many elements and atoms are in that compound. Calculate the molecular mass or molar mass of any compound. State that the mass of a molecule is measured in amu s and the mass of a mole is measured in grams. Give examples of empirical formulas, molecular formulas, and structural formulas. Identify a formula as empirical, molecular, or structural. Ionic Compounds I can: List the names and formulas of 60 ions. State whether a compound is an ionic compound or a nonmetal compound. Write the formula of an ionic compound given the two ions or its name. Know when to use parentheses. Name an ionic compound given the formula. Determine the charge on an ion from information in an ionic formula. Nonmetal Compounds aka Molecular Compound Write the formula of a binary nonmetal compound (molecular compound) given its name. Name a binary nonmetal compound (molecular compound) given its formula. Name STUDY LIST Percent Composition Calculate the percent composition (by mass) for any compound. Calculate the empirical formula from percent composition data. Determine the molecular formula of a compound given its empirical formula and molar mass. Hydrates Give examples of hydrates and anhydrous compounds. Calculate the formula of a hydrate from dehydration data. The Mole State the significance of the mole. State the three mole facts for any substance (molar volume, molar mass, Avogadro s number) 1 mole 22.4 STP (gases only) 1 mole 6.02 x particles (particles molecules or atoms) 1 mole gram molecular mass of chemical Use dimensional analysis to convert between moles, mass, volume, and number of particles for a chemical. Use density as a conversion factor in mole problems. Use gas density to calculate molar mass.

2 Keep for Reference FIRST 40 IONS TO MEMORIZE aluminum Al 3+ strontium Sr 2+ ammonium NH 4 + stannous Sn 2+ barium Ba 2+ stannic Sn 4+ calcium Ca 2+ zinc Zn 2+ cuprous Cu + acetate C 2 H 3 O 2 or CH 3 COO cupric Cu 2+ bromide Br ferrous Fe 2+ carbonate 2 CO 3 ferric Fe 3+ chlorate ClO 3 hydrogen H + chloride Cl hydronium H 3 O + chromate 2 CrO 4 lead Pb 2+ dichromate 2 Cr 2 O 7 lithium Li + fluoride F magnesium Mg 2+ hydroxide OH manganese Mn 2+ iodide I mercurous Hg 2 2+ nitrate NO 3 mercuric Hg 2+ oxide O 2 nickel Ni 2+ permanganate MnO 4 potassium K + phosphate 3 PO 4 silver Ag + sulfate 2 SO 4 sodium Na + sulfide S 2

3 H I II III IV V VI VII Li O F Na Mg Al S Cl K Ca Br VIII Name ates ORGANIZE YOUR IONS Sr I Ba 1+ ions 1- ions 2+ ions 2- ions 3- ions Elements with two different ion names / charges 3+ ions 4+ ions

4 3 Molecules & Compounds Name Writing Formulas and Naming Compounds Introduction Writing formulas and naming compounds can be confusing because there are different types of compounds that follow different rules. Additionally, some compounds (H 2 O, NH 3, CH 4, etc.) simply have common names that must be memorized. The two types of compounds we will focus on first are ionic compounds (formed from positive and negative ions) and binary nonmetal compounds (molecular compounds). Later we will add acids. So you must recognize the type of compound before you try to name it. [Note: + ion cation and ion anion.] Formula Naming Ionic + ion before ion ex: NaCl (NH 4 ) 2 SO 4 Al 2 S 3 Name of cation + name of anion sodium chloride ammonium sulfate aluminum sulfide Binary Nonmetal usually the less electronegative atom is first ex: CO CO 2 N 2 O Indicate the number (mono, di, tri, and kind of atoms. First element is simply name of element. Second element name ends with ide carbon monoxide carbon dioxide dinitrogen monoxide I. Writing Ionic Formulas Cl NO 3 S 2 CO 3 2 N 3 PO 4 3 OH Na + NH 4 + Sn 2+ Hg 2 2+ Al 3+ Sn 4+ II. Naming Ionic Compounds Cation Anion Formula Name Cu 2+ OH Ba 2+ 2 SO 4 NH 4 + Cr 2 O 7 2 Ag + C 2 H 3 O 2 Fe 3+ S 2

5 mono di tri tetra penta hexa hepta octa nona deca III. Writing Formulas of Binary Nonmetal Compounds Name Formula Name Formula nitrogen trifluoride nitrogen monoxide nitrogen dioxide dinitrogen tetroxide dinitrogen monoxide phosphorus trichloride phosphorus pentachloride sulfur hexafluoride disulfur decafluoride xenon tetrafluoride IV. Naming Binary Nonmetal Compounds Name Formula Name Formula CCl 4 HBr P 4 O 10 N 2 F 4 ClF 3 XeF 3 BCl 3 PI 3 SF 4 SCl 2 V. Practice for Both Types of Compounds Formula Name Formula Name HCl PCl 5 K 2 S NiSO 4 ClF 3 OF 2 Al(OH) 3 NCl 3 (NH 4 ) 3 PO 4 S 2 Cl 2 carbon dioxide ammonium carbonate sulfur dichloride calcium iodide boron trifluoride phosphorus triiodide magnesium perchlorate potassium permanganate aluminum phosphate dioxygen difluoride

6 3 Molecules & Compounds 1 mole 6.02 x molecules 22.4 L (@ STP) 1. Calculate the mass of 1.58 moles CH 4. [molar mass CH g/mol] 1.58 moles CH 4? g CH moles CH4 Name Mole Calculations - Difficulty Level 1 2. What volume will 7.29 moles of CO 2 gas occupy at STP? 7.29 moles CO 2? L CO moles CO2 3. How many molecules are there in a mole sample of H 2 O? moles H 2 O? molecules H 2 O moles H2O 4. What mass of CO 2 gas occupies a volume of 100. Liters at STP? [molar mass CO g/mol] 100. Liters CO 2? g CO Liters CO2 5. How many molecules are in a 35.0 gram sample of H 2 O? [molar mass H 2 O 18.0 g/mol] 35.0 g H 2 O? molecules H 2 O 35.0 g H2O 6. What volume will 5.25 x molecules of CH 4 occupy at STP? 5.25 x molecules CH 4? L 5.25 x molecules CH4

7 3 Molecules & Compounds 1 mole 6.02 x molecules 22.4 L (@ STP) 1. Calculate the mass of 2.19 moles CH 4. [molar mass CH g/mol] 2. What volume will 2.22 moles of CO 2 gas occupy at STP? 3. How many molecules are there in a mole sample of H 2 O? Name Mole Calculations - Difficulty Level 2 4. What mass of CO 2 gas occupies a volume of 395 Liters at STP? [molar mass CO g/mol] 5. How many molecules are in a gram sample of H 2 O? [molar mass H 2 O 18.0 g/mol] 6. What volume will 3.01 x molecules of CH 4 occupy at STP?

8 3 Molecules & Compounds 1 mole 6.02 x molecules 22.4 L (@ STP) 1. Calculate the mass of 7.23 moles CH 4. [molar mass CH g/mol] Name Mole Calculations - Difficulty Level 3 2. What volume will 9.35 moles of CO 2 gas occupy at STP? 3. How many molecules are there in a mole sample of H 2 O? 4. What mass of CO 2 gas occupies a volume of 10.8 Liters at STP? [molar mass CO g/mol] 5. How many molecules are in a 1.44 gram sample of H 2 O? [molar mass H 2 O 18.0 g/mol] 6. What volume will 1.21 x molecules of CH 4 occupy at STP?

9 Name Period Date / / MOLAR MASS & % COMPOSITION I. Molar Masses Given a periodic table, you should be able to calculate the molecular mass (in u s) or the molar mass (in grams) for any element or compound. Examples: (give answers to two decimal places) H 2 SO 4 Cl 2 Ca(OH) 2 HC 2 H 3 O 2 CO 2 N 2 O NaOCl Al 2 S 3 II. Fraction and Percent Composition It is useful to determine how much of a compound s mass is made up of each element. Water, H 2 O, for example has a molar mass of g. The H s mass is 2(1.0079) 2.02 g. The O s mass is g We can set up fractions for each element: H %. O % This is called the percent composition. The fraction composition is a good in-between step. Determine the fraction and percent composition of each element below (answer to one decimal place): 1. H 2 SO 4 2. Ca(OH) 2 3. HC 2 H 3 O 2 4. CO 2 5. N 2 O 6. NaOCl 7. Al 2 S 3

10 Name HYDRATES & COMPOSITION PROBLEMS 1. Cupric chloride, CuCl 2, when heated to 100 C is dehydrated. If g of CuCl 2 x H 2 O gives g of CuCl 2 on heating, what is the value of x? 2. The alum used in cooking is potassium aluminum sulfate hydrate, KAl(SO 4 ) 2 x H 2 O. To find the value of x, you can heat a sample of the compound to drive off all of the water and leave only KAl(SO 4 ) 2. Assume you heat 4.74 g of the hydrated compound and that the sample loses 2.16 g of water. What is the value of x? 3. If Epsom salt, MgSO 4 x H 2 O is heated to 250 C, all the water of hydration is lost. On heating a g sample of the hydrate, g of MgSO 4 remains. What is the formula of Epsom salt? 4. When CaSO 4 x H 2 O is heated, all of the water is driven off. If 34.0 g of CaSO 4 (molar mass 136) is formed from 43.0 g of CaSO 4 x H 2 O, what is the value of x?

11 Name QUICK CHECK #1 Try these problems. If you can DO them, check the box ( ). If you CANNOT do them, write some notes TO YOURSELF about what you need to study to succeed at these problems. List the 7 diatomic elements Mini Ion Quiz (fill in the missing information): Name Formula & Charge Name Formula & Charge aluminum fluoride cupric hydroxide sulfide sulfate + NH 4 NO 3 2- Cr 2 O 7 C 2 H 3 O 2 Show your work for this problem: A slab of metal has a density of 6.50 g/cm 3 and a volume of Liters. Calculate the mass (in kg) of this slab of metal. Recall that there are 1000 cm 3 in a Liter Liters x x x

12 Name QUICK CHECK #2 Try these problems. If you can DO them, check the box ( ). If you CANNOT do them, write some notes TO YOURSELF about what you need to study to succeed at these problems. List the 7 diatomic elements Name the following compounds (which of these are empirical formulas?) Hg 2 I 2 PCl 3 SO 3 NH 4 NO 3 Fill in this chart: Name Cation Anion Formula magnesium phosphate silver sulfide aluminum hydroxide Calculate the percent composition of NH 4 NO 3 N H O

13 Name QUICK CHECK #3 Try these problems. If you can DO them, check the box ( ). If you CANNOT do them, write some notes TO YOURSELF about what you need to study to succeed at these problems. Molar Mass Calculate the molar mass of NO 2 (g). Give mass to two decimal places. Mole Problem (show work as a dimensional analysis problem) Calculate the mass of NO 2 (g) that will fit into a 2.00 Liter bottle at STP. Given: Desired: Another Mole Problem A sample of NO 2 (g) has a mass of kg. How many molecules is this?

14 Name the following compounds: Formula BF 3 Name Name Station 1 NAMING COMPOUNDS FROM FORMULAS SF 6 (NH 4 ) 2 Cr 2 O 7 PbCO 3 NI 3 South Pasadena AP Chemistry Station 2 WRITING FORMULAS FROM NAMES Write the formulas for the following compounds: Name Dinitrogen pentoxide Formula Aluminum oxide Stannic sulfate Oxygen difluoride Carbon tetrachloride

15 South Pasadena AP Chemistry Fill in the symbol and charge for each of the following ions: Station 3 MINI MEGA-ION QUIZ ferric sulfite hydronium permanganate silver hydroxide sulfide thiosulfate cupric phosphate hypoiodite mercurous calcium nickel cyanide South Pasadena AP Chemistry Station 4 MYSTERY IONS Use your knowledge of ions and a little logic to answer the following questions: Sodium arsenide has the formula: Na 3 As. What is the formula for magnesium arsenide? Gold sulfide has the formula: Au 2 S 3. What is the formula for gold chloride? Calcium oxalate has the formula: CaC 2 O 4. What is the formula for aluminum oxalate?

16 South Pasadena AP Chemistry Station 5 % COMPOSITION Use your periodic table and calculator to determine the % composition (by mass) of each element in: Note: Give your answers to 1 decimal place. Formula %Ca %C %N Ca(CN) 2 Calculation Area: South Pasadena AP Chemistry Station 6 EMPIRICAL FORMULA FROM % COMPOSITION Determine the empirical formula of the compound from the following %composition (by mass) information: A compound composed of carbon and hydrogen is found to contain 85.6% C and 14.4% hydrogen by mass. What is the empirical formula of the compound? Calculation Area:

17 South Pasadena AP Chemistry Station 7 MOLE PROBLEMS Solve the following problems. Show your work using dimensional analysis: A 2.00 Liter bottle is filled with XeF 4 gas. What is the mass of the gas sample? [MM XeF g/mol] How many molecules of CO 2 make up a 5.25 g chunk of dry ice? [MM CO g/mol] South Pasadena AP Chemistry Station 8 IDENTIFY MYSTERY SUBSTANCE When asked to identify a mystery compound, it is often useful to determine the molar mass of the substance. Use the following information to identify the mystery substance: A 1.25 Liter sample of a diatomic gas, measured at STP, has a mass of 3.96 grams. What is the identity of the gas?

18 South Pasadena AP Chemistry Station 9 HYDRATE LAB A student is assigned the task of determining the number of moles of water in one mole of MgCl 2 n H 2 O. The student collects the data shown in the following table. Mass of empty container Initial mass of sample and container Mass of sample and container after first heating Mass of sample and container after second heating Mass of sample and container after third heating g g g g g Determine the moles of water lost when the sample was heated. Determine the formula of the hydrated compound. South Pasadena AP Chemistry Station 9 HYDRATE LAB A student is assigned the task of determining the number of moles of water in one mole of MgCl 2 n H 2 O. The student collects the data shown in the following table. Mass of empty container Initial mass of sample and container Mass of sample and container after first heating Mass of sample and container after second heating Mass of sample and container after third heating g g g g g Determine the moles of water lost when the sample was heated. Determine the formula of the hydrated compound.

19 Name STUDY QUESTIONS and PROBLEMS 1. a. The structural formula for acetic acid is CH 3 CO 2 H. What is its empirical formula; what is its molecular formula? b. The molecular formula of acrylonitrile is C 3 H 3 N. Look up in the text, and draw, its structural formula. c. The molecular formula of aspartame (nutrasweet) is C 14 H 18 O 5 N 2. Look up in the text, and draw, its structural formula. 2. The formulas for ethanol and ammonium nitrate are C 2 H 5 OH and NH 4 NO 3. In what respects are these formulas and compounds different? 3. The molecular formula for both butanol and diethylether is C 4 H 10 O. Write structural formulas for both and show how they are different. Are any other structures possible? 4. Name the polyatomic ions: CH 3 CO 2 - H 2 PO 4 - SO What are the formulas of the polyatomic ions: phosphate sulfate bisulfite nitrite cyanide chlorite HCO 3 - Cr 2 O 7 2- ClO 4-6. Write the ions present in the following salts and predict their formulas: potassium bromide calcium carbonate magnesium iodide lithium oxide aluminum sulfate ammonium chlorate beryllium phosphate 7. Name the following ionic salts: (NH 4 ) 2 SO 4 KHCO 3 Ca(NO 3 ) 2 Co 2 (SO 4 ) 3 NiSO 4 AlPO 4 8. Name the following binary compounds of the nonmetals: CS 2 SF 6 IF 5 N 2 H 4 PCl 5 Cl 2 O 7 SiCl 4 GeH 4 P 4 O 10 S 4 N 4 OF 2 IF 7

20 9. What are the formulas for the following binary compounds? silicon dioxide phosphine boron trifluoride silicon carbide xenon tetroxide phosphorus tribromide dinitrogen pentoxide disulfur dichloride bromine trifluroide hydrogen selenide carbon tetrachloride 10. a. How many moles are present in 128 grams of sulfur dioxide? b. What is the mass of 3 moles of oxygen molecules? c. If 5 moles of a metallic element have a mass of 200 grams, which element is it? d. What is the molar mass of methane CH 4? e. What is the mass of 9 moles of fluorine molecules? f. 102 grams of a gas contains 6 moles. What is its molar mass? g. How many grams are there in one mole of benzene C 6 H 6? h. How many moles of nitrogen atoms are there in 6 moles of TNT (trinitrotoluene CH 3 C 6 H 2 (NO 2 ) 3 )? i. What is the molar mass of TNT? 11. What is the percent by mass of nitrogen in ammonium nitrate? 12. The hydrocarbons ethylene (molar mass 28 g/mol), cyclobutane (molar mass 56 g/mol), pentene (molar mass 70 g/mol), and cyclohexane (molar mass 84 g/mol), all have the same empirical formula. What is it? Write the molecular formulas for these four compounds. 13. A compound was analyzed and found to contain 76.57% carbon, 6.43% hydrogen, and 17.00% oxygen by mass. Calculate the empirical formula of the compound. If the molar mass of the compound is 94.11g/mol, what is the molecular formula of the compound? 14. A compound was analyzed and found to contain 53.30% carbon, 11.19% hydrogen, and 35.51% oxygen by mass. Calculate the empirical formula of the compound. If the molar mass of the compound is g/mol, what is the molecular formula of the compound? 15. A g sample of a hydrate of magnesium carbonate was carefully heated, without decomposing the carbonate, to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate? 16. Anhydrous lithium perchlorate (4.78 g) was dissolved in water and re-crystallized. Care was taken to isolate all the lithium perchlorate as its hydrate. The mass of the hydrated salt obtained was 7.21 g. What hydrate is it?