Stoichiometry

Your Job Using the worksheet in your packet…. Write what is in BLUE in the box titled “notes” Write the steps to solving problems and example problems on bottom half of worksheet. If you need more room, use the back of your packet.

What is stoichiometry? The study of the quantitative aspect of chemical reactions

Why do we care? Just like a cookie recipe needs the exact amounts of ingredients to make a perfect batch, so do chemical reactions! Using stoichiometry, we can calculate how much product you’ll produce from a given amount of reactants, or how many reactants you need to form a certain amount of products.

Writing and using mole ratios N2 + 3H2 -> 2NH3 -Balanced chem equations provide a lot of quantitative information. -It relates particles (atoms, molecules, formula units) moles of a substance, and masses. -A balanced equation is essential to calculate amounts of reactants and products. -Mole ratio: conversion factor derived from coefficients of a balanced chemical equation interpreted in terms of moles. -In chemical calculations, more ratios are used to convert between moles of reactant and moles of product. Write the mole ratios for the formation of ammonia:

Try some!

Using Chemical Calculations 3 main types of chemical calculations Mole-mole Mass-mole, mole-mass Mass-mass All calculations will require a balanced chem. equation and mole ratios Tips in solving problems: Always write your “given” first! Always set up your units so you can cancel them out Place the units you want on top of the conversion factor

Mole-Mole Calculations N2 + 3H2 -> 2NH3 Given moles x # mol unknown = mol unknown # mol given How many moles of ammonia are produced when .60 mol of nitrogen reacts with hydrogen? How many moles of nitrogen are needed to produce 1.8 mol ammonia?

Moles-Grams (moles-mass) Calculations N2 + 3H2 -> 2NH3 Given moles x # mol unknown x m. mass unknown = mass (grams) unknown # mol given 1 mol unknown How many grams of nitrogen are needed to react completely with 2.5 moles of hydrogen? How many grams of ammonia are produced when .75 mole of hydrogen react with an excess of nitrogen?

Grams-Moles (mass-moles) Calculations N2 + 3H2 -> 2NH3 Given grams x 1 mole given x # mol unknown = # mole unknown m. mass given (g) # mol given How many moles of nitrogen when combined with 27 grams hydrogen are needed to form ammonia? How many moles of hydrogen are needed to form 105 grams of ammonia?

Grams-Grams (mass-mass) Calculations N2 + 3H2 -> 2NH3 Given grams x 1 mol given x # mol unknown x m. mass unknown (g) = mass unknown(g) m. mass given (g) # mol given 1 mol unknown Calculate the number of grams of ammonia produced by the reaction of 5.40g hydrogen with an excess of nitrogen. Calculate the number of grams of nitrogen when 55g hydrogen are added to form ammonia.

How are we doing?

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