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CP Chemistry Review Sheet for Mass – Moles – Particles Mass to Moles Must Get Moles to Mass 1. 2. 3. Molecules are made of atoms bonded together. 1 mole of a compound has 6.02x1023 molecules in it 1 mole of a compound = it’s G. F. M Don’t just plug in numbers, ask yourself what the problem is asking and what type of answer you should get ( higher or lower than you started with) When changing from one unit to another, you must use a conversion factor which is a ratio where the top is equal to the bottom; both numbers have units The conversion factor changes the unit Dimensional Analysis is the process of using conversion factors to solve problems to change one unit to another. Every problem is different. DO NOT MEMORIZE PROBLEMS, but learn to problem solve. 1. Read the problem 2. Re-read the problem, circling the given information. Put an ‘X’ over what you need to find out. Key words for this sometimes are “How much, how many, What mass” 3. Re-write the problem in the following format: Unit you want to change = X units ***Hint: Unit to be changed will never be part of a defined ratio in the problem 4. Write down all ratios defined in problem or that you know might need to be used in problem based on information/units you circled when you read the problem. 5. Start with the unit you want to change and multiply it by a conversion factor so the unit you want to get rid of is on the bottom and the unit you want to change to is on top. unit 1 unit 2 unit 1 PRACTICE PROBLEMS: 1. My dad is gong to make me bookshelves for 305 books. Each bookshelf has 5 shelves and each shelf can hold 25 books. How many bookshelves will he have to build? 2. 2.5 moles of Zn = ? atoms Zn? 3. How many grams are 1.2x1024 molecules of CO2? 4. How many atoms are containted in 3 molecules of CH4? 5. How much does 0.15 moles of sulfur weigh? 6. What conversion factor would be used to change moles of water to molecules? 7. What is the molar mass of (NH4)2SO4? 8. How many atoms are contained in 0.75 g of NO2? 1) 3 2) 1.5x1024 atoms 3) 88g 4)15atoms 5)4.8g 6) 6.02x1023/1mole 7) 132 g/mole 8) 2.94 x 10 22