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Stoichiometry

Stoichiometry. What is stoichiometry ?. Stoichiometry is the study of the quantitative, or measurable , relationships that exist in chemical formulas and chemical reactions. ( Calculations that relate quantities of substances are known as stoichiometry problems.).

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Stoichiometry

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  1. Stoichiometry

  2. What is stoichiometry? Stoichiometryis the study of the quantitative, or measurable, relationships that exist in chemical formulas and chemical reactions. (Calculations that relate quantities of substances are known as stoichiometry problems.)

  3. The Meaning of the Word The word stoichiometry derives from two Greek words: stoicheion (meaning "element") and metron(meaning "measure"). Stoichiometry deals with calculations about the masses (sometimes volumes) of reactants and products involved in a chemical reaction. It is a very mathematical part of chemistry, so be prepared for lots of calculator use.

  4. JeremiasBenjaim Richter • JeremiasBenjaim Richter(1762-1807) was the first scientist to introduce the principles of stoichiometry. • In 1792 he wrote: "Stoichiometry is the science of measuring the quantitative proportions or mass ratios in which chemical elements stand to one another.”

  5. Molar Ratios In a balanced equation, the coefficients indicate the number of particles of each substance taking part in the reaction. These coefficients can be used to determine the ratio of moles, or molar ratios. Molar ratiosare essential for solving any stoichiometry problem.

  6. EXAMPLE CH4  +   2O2  CO2   + 2H2O What is the molar ratio of CH4 to H2O? What is the molar ratio of O2 to CO2? What is the molar ratio of H2O to O2?

  7. MOLE – MOLE PROBLEMS Mole-mole problems are problems where you convertfrom moles of one substance to moles of another substance. The ability to convert moles of one substance in a reaction to moles of another substance in a reaction is also essential for solving more complex types of stoichiometry problems.

  8. EXAMPLE How many moles of HCl are needed to react with 2.3 moles of Zn? 2HCl + Zn  ZnCl2 + H2 (Moles of given x molar ratio) 2.3 mol Zn x _2_HCl____ = 4.6 mol HCl 1 1 1 Zn

  9. PRACTICE PROBLEMS Magnesium burns in oxygen to produce magnesium oxide. How many moles of oxygen are needed to burn 0.52 mole of magnesium? 2Mg + O2 2MgO

  10. How many moles of Al(NO2)3will be produced when 0.75 mol AgNO2reacts according to the following equation: 3AgNO2 + Al  Al(NO2)3 + 3Ag

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