# Unit 6 Stoichiometry Section 3 Stoichiometry Mole Mole

- Slides: 20

Unit 6: Stoichiometry Section 3: Stoichiometry - Mole: Mole and Gram: Gram

Stoichiometry • Branch of chemistry that involves using known ratios of products and reactants to determine unknown data in a chemical reaction – Chemists use stoichiometry conversions like cooks use cooking recipes • Ratio for these conversions can be found in the balanced equation!! (Coefficients!)

Mole-to-Mole Formula • When converting from moles of one substance to moles of another • “G” stands for “given” chemical • “U” stands for “unknown” chemical Use the coefficient from the balanced equation

Mole-to-Mole Problems Ex-1: If you want to manufacture 150 moles of ammonia (NH 3), how many moles of hydrogen will you need? H 2 + N 2 → NH 3 Step 1: Balance the equation 3 H 2 + N 2 → 2 NH 3

Mole-to-Mole Problems Ex-1: If you want to manufacture 150 moles of ammonia (NH 3), how many moles of hydrogen will you need? 3 H 2 + N 2 → 2 NH 3 Step 2: Identify the “given” and “unknown” from the problem with units. G: 150 mol NH 3 U: # mol H 2

Mole-to-Mole Problems Ex-1: If you want to manufacture 150 moles of ammonia (NH 3), how many moles of hydrogen will you need? 3 H 2 + N 2 → 2 NH 3 G: 150 mol NH 3 U: # mol H 2 Step 3: Set up a conversion factor with given units in the bottom: 150 mol NH 3 x _______ mol NH 3

Mole-to-Mole Problems Ex-1: If you want to manufacture 150 moles of ammonia (NH 3), how many moles of hydrogen will you need? 3 H 2 + N 2 → 2 NH 3 G: 150 mol NH 3 U: # mol H 2 Step 4: The unit on top must be the unit you want; same as your “unknown” 150 mol NH 3 x mol H 2 mol NH 3

Mole-to-Mole Problems Ex-1: If you want to manufacture 150 moles of ammonia (NH 3), how many moles of hydrogen will you need? 3 H 2 + N 2 → 2 NH 3 G: 150 mol NH 3 U: # mol H 2 Step 5: Plug in the coefficients from the balanced equation: 150 mol NH 3 x 3 mol H 2 = 225 mol H 2 2 mol NH 3

Mole-to-Mole Problems Ex-1: If you want to manufacture 150 moles of ammonia (NH 3), how many moles of Hydrogen will you need? 3 H 2 + N 2 → 2 NH 3 G: 150 mol NH 3 U: # mol H 2 Step 6: Round answer to the correct number of significant figures and include your unit!!!! 150 mol NH 3 x 3 mol H 2 = 225 mol H 2 → 230 mol H 2 2 mol NH 3

Mole-to-Mole Practice Ex-2: If you want to make 100 moles of ammonia (NH 3), how many moles of Nitrogen (N 2) will you need? 3 H 2 + N 2 → 2 NH 3 50 mol N 2

Mole-to-Mole Practice Ex-3: If you have 36 moles of nitrogen (N 2), how many moles of hydrogen (H 2) will you need? 3 H 2 + N 2 → 2 NH 3 110 mol H 2

Gram-to-Gram Formula • Used to figure out the # of grams of one substance needed to make another • “U” = “unknown”; “G” = “given” Use the coefficient from the balanced equation OMG ITS THE SAME AS THE MOLE TO MOLE FORMULA!

Gram-to-Gram Problems Ex-1: How many grams of glass (Si. O 2) can be etched by 100 grams of hydrofluoric acid (HF)? HF + Si. O 2 → Si. F 4 + H 2 O Step 1: Balance the equation 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O

Gram-to-Gram Problems Ex-1: How many grams of glass (Si. O 2) can be etched by 100 grams of hydrofluoric acid (HF)? 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O Step 2: Identify the “given” and “unknown” from problem with units G: 100 g HF U: # g Si. O 2

Gram-to-Gram Problems Ex-1: How many grams of glass (Si. O 2) can be etched by 100 grams of hydrofluoric acid (HF)? 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O Step 3: Set up a conversion factor with the given units in the bottom… this will be its molar mass. The numerator will always be 1 mole of the “given” chemical 100 g HF x 1 mol HF 20. 008 g HF

Gram-to-Gram Problems Ex-1: How many grams of glass (Si. O 2) can be etched by 100 grams of hydrofluoric acid (HF)? 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O Step 4: Next, use a mole-to-mole conversion factor to go from one chemical to the other. Take the numbers for the coefficients from the balanced equation. 100 g HF x 1 mol Si. O 2 20. 008 g HF 4 mol HF

Gram-to-Gram Problems Ex-1: How many grams of glass (Si. O 2) can be etched by 100 grams of hydrofluoric acid (HF)? 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O Step 5: We need our answer in grams, so do a basic mole-to-gram conversion (1 mole on bottom; molar mass on top) 100 g HF x 1 mol Si. O 2 x 60. 09 g Si. O 2 = 75. 082 20. 008 g HF 4 mol HF 1 mol Si. O 2

Gram-to-Gram Problems Ex-1: How many grams of glass (Si. O 2) can be etched by 100 grams of hydrofluoric acid (HF)? 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O Step 6: Make sure your final answer is in the correct # of sig figs with its unit 100 g HF x 1 mol Si. O 2 x 60. 083 g Si. O 2 = 75. 082 20. 0059 g HF 4 mol HF 1 mol Si. O 2 80 g Si. O 2

Gram-to-Gram Practice Ex-2: How many grams of glass (Si. O 2) can be made from 230 grams of H 2 O? 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O 380 g Si. O 2

Gram-to-Gram Practice Ex-3: How many grams of Silicon fluoride (Si. F 4) are needed to make 100. 50 g of water? 4 HF + Si. O 2 → Si. F 4 + 2 H 2 O 290. 33 g Si. F 4

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