Warm Up Write the electron configuration for Br- Using the noble gas configuration The non condensed configuration Show the energy levels with arrows (hund’s rule)

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Part 3: Mole Calculations We can use moles and formula mass to work out mass of chemicals needed/used M = n X FM n = M/FM FM = M/n (n)

Example If I have 9g of water, how many moles do I have? n = M/FM n = 9g/18 n = 0.5 What is the mass of 0.25 moles N2? (n) M = n X FM M = 0.25 X 28 M = 7g

Working out the formula 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound?

Working out the formula 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound? First work out the number of moles 1.4g Nitrogen = mass/AM = 1.4/14 = 0.1 0.3g hydrogen = mass/AM = 0.3/1 = 0.3

Working out the formula 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound? Work out the ratio of the number of moles of each element to the lowest whole numbers N : H 0.1 : 0.3 1 : 3

Working out the formula 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound? Therefore there are 3 times as many hydrogen atoms as N atoms in the compound. The formula must be NH3 (ammonia)

Do You Understand Molecular Mass? How many moles of H are in 72.5 g of C3H8O ?

Mass and Moles of a Substance Mole calculations Suppose we have 3.25 moles of glucose, C6H12O6. What is its mass? 2

2NaOH + Cl2  NaOCl + NaCl + H20 Using equations 2NaOH + Cl2  NaOCl + NaCl + H20 If we have a solution containing 100g of NaOH, how much chlorine gas should we pass through the solution to make bleach (NaOCl)?

2NaOH + Cl2  NaOCl + NaCl + H20

Hydrates

PROBLEM: Calculate the % by mass of water in one mole of BaCl2•2H2O % H2O in a Hydrate Certain substances have water molecules associated with their structure. Many salts fall into this category and we refer to them as hydrated salts. Different salts have different numbers of water molecules - BaCl2•2H2O; CuSO4•5H2O. PROBLEM: Calculate the % by mass of water in one mole of BaCl2•2H2O %H2O = (mass of H2O in one Mol/mass of BaCl2•2H2O) x 100 %H2O = (36 grams/243 grams) x 100 = 14.8% H2O

Review

Naming monatomic cations – alkali and alkaline-earth metals. A. Naming ions for alkali and alkaline-earth metals is easy. Just use the element’s name plus the word ion (or cation if you prefer).   Atom Ion formed Ion name Li ________ ____________________________ Na ________ ____________________________ Mg ________ ____________________________ Ca ________ ____________________________

Molecular Formula   Molecular Formula = Actual Formula Example: C2H6 CH3 molecular empirical MF = (EF)x where X = Molecular mass Empirical mass The empirical formula of a compound was found to be P2O5. Experimentation shows that the molar mass of this compound is 283.89 g/mol. What is the compound’s molecular formula?