# Math in Science Working in Steps Chemistry Complications.

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Math in Science Working in Steps Chemistry Complications

Prompt If you react 25.0 g of H 2 gas with more than enough O 2 gas – How much water will result? In grams, ( in ml, Sip / Swallow / Gulp?

Step 1 Balance the EquationBalance the Equation. Every atom on the left has to be represented / equal in number on the right… H 2 + O 2 H 2 O 2H 2 + O 2 2H 2 O

Step 2 Convert to MolesConvert to Moles Moles = grams / molar mass Molar mass = the mass of a mole of the substance. Molar mass of H = 1 g/mole -- What is the molar mass of H 2 ? Moles of Hydrogen = 25.0g / 2 g/mole 12.5 Moles H2 2 Hydrogens means 2 x 1 g/mole = 2 g/mole

Step 3 Use the Ratio (Luke) 2H 2 + O 2 2H 2 O 2: 1 : 2 2 H 2 = 2 H 2 O 25H 2 x H 2 O x = 25 Moles of H 2 O

Step 4 Convert to … Convert to … (in this case, grams) Grams = Moles x Molar Mass (Whats the Molar Mass of Water?) 2 Hydrogens, 1 Oxygen 1+1+16 Grams = 25 moles x 18 g/mole x = 25 Moles of H 2 O

Oh dear, bust out the calculator…25 x 18 = 450 g of Water… (= 450 ml of water = some serious chugging! More than a soda cans worth)

Want Another??? If I burn 15 g of Steel Wool (Fe) – How much Iron Oxide should result (in grams)? Complications – there are 2 possible reactions Fe + O 2 FeO Fe + O 2 Fe 2 O 3 (not balanced )