1 / 17

7.7 Mass Calculations for Reactions

7.7 Mass Calculations for Reactions. A mixture of acetylene and oxygen undergoes combustion during the welding of metals. We can calculate the mass of acetylene used to weld a specific mass of metal.

linaeve
Download Presentation

7.7 Mass Calculations for Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. 7.7 Mass Calculations for Reactions A mixture of acetylene and oxygen undergoes combustion during the welding of metals. We can calculate the mass of acetylene used to weld a specific mass of metal. Learning Goal Given the mass in grams of a substance in a reaction, calculate the mass in grams of another substance in the reaction.

  2. Equations, Mass of A−Mass of B • Given a balanced equation, convert the mass of substance A to substance B by • first, converting the mass of substance A to moles using the molar mass of A; • second, converting moles of substance A to moles of substance B using the mole–mole ratio of B to A in the balanced equation; and • third, converting moles of substance B to grams using the molar mass of B.

  3. Equations, Mass of A−Mass of B Core Chemistry Skill Converting Grams to Grams

  4. Mass N2 − Mass NH3 Suppose we want to determine the mass (grams) of NH3 that can be produced from 32 grams of N2 in the following equation. N2(g) + 3H2(g)  2NH3(g) STEP 1State the given and needed quantities. ANALYZE Given Need THE PROBLEM 32 g N2 mass (grams) NH3 N2(g) + 3H2(g)  2NH3(g)

  5. Mass N2 − Mass NH3 Suppose we want to determine the mass (grams) of NH3 that can be produced from 32 grams of N2 in the following equation. N2(g) + 3H2(g)  2NH3(g) STEP 2 Write a plan to convert the given to the needed quantity (grams). grams moles moles grams N2 N2 NH3 NH3 Molar mass N2 Mole–mole factor NH3/N2 Molar mass NH3

  6. Mass N2 − Mass NH3 Suppose we want to determine the mass (grams) of NH3 that can be produced from 32 grams of N2 in the following equation. N2(g) + 3H2(g)  2NH3(g) STEP 3 Use coefficients to write mole–mole factors; write molar mass factors if needed.

  7. Mass N2 − Mass NH3 Suppose we want to determine the mass (grams) of NH3 that can be produced from 32 grams of N2 in the following equation. N2(g) + 3H2(g)  2NH3(g) STEP 4Set up the problem to give the needed quantity (grams). • Exact • Exact • Four SFs × × × • Two SFs • Four SFs • Exact • Exact • Two SFs

  8. Study Check How many grams of O2 are needed to produce 45.8 grams of Fe2O3 in the following reaction? 4Fe(s) + 3O2(g)  2Fe2O3(s) A. 38.4 g of O2 B. 13.8 g of O2 C. 1.38 g of O2

  9. Solution How many grams of O2 are needed to produce 45.8 grams of Fe2O3 in the following reaction? 4Fe(s) + 3O2(g)  2Fe2O3(s) STEP 1State the given and needed quantities. ANALYZE Given Need THE PROBLEM 45.8 g Fe2O3 mass (grams) O2 4Fe(s) + 3O2(g)  2Fe2O3(s)

  10. Solution How many grams of O2 are needed to produce 45.8 grams of Fe2O3 in the following reaction? 4Fe(s) + 3O2(g)  2Fe2O3(s) STEP 2 Write a plan to convert the given to the needed quantity (grams). grams moles moles grams Fe2O3 Fe2O3 O2 O2 Molar mass Fe2O3 Molar mass O2 Mole–mole factor O2/Fe2O3

  11. Solution How many grams of O2 are needed to produce 45.8 grams of Fe2O3 in the following reaction? 4Fe(s) + 3O2(g)  2Fe2O3(s) STEP 3 Use coefficients to write mole–mole factors; write molar mass factors if needed.

  12. Solution How many grams of O2 are needed to produce 45.8 grams of Fe2O3 in the following reaction? 4Fe(s) + 3O2(g) 2Fe2O3(s) STEP 4Set up the problem to give the needed quantity (grams). The answer is B. • Four SFs • Exact • Exact × × × • Exact • Three SFs • Exact • Three SFs • Five SFs

  13. Study Check The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted? 2H2(g) + O2(g)  2H2O(g)

  14. Solution The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted? 2H2(g) + O2(g)  2H2O(g) STEP 1State the given and needed quantities. ANALYZE Given Need THE PROBLEM 13.1 g H2O mass (grams) O2 2H2(g) + O2(g)  2H2O(g)

  15. Solution The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted? 2H2(g) + O2(g)  2H2O(g) STEP 2 Write a plan to convert the given to the needed quantity (grams). grams moles moles grams H2OH2OO2 O2 Molar mass H2O Mole–mole factor O2/H2O Molar mass O2

  16. Solution The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted? 2H2(g) + O2(g) 2H2O(g) STEP 3 Use coefficients to write mole–mole factors; write molar mass factors if needed.

  17. Solution The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted? 2H2(g) + O2(g)  2H2O(g) STEP 4Set up the problem to give the needed quantity (grams). • Exact • Exact • Four SFs × × × • Three SFs • Four SFs • Exact • Exact • Three SFs

More Related