1. Chemical Masses and Formulas L.O: To know how to work out the empirical formula of compounds

2.  We found 5.5g of manganese reacted with 3.2g of oxygen. What is the formula of the oxide of manganese formed? (Atomic. Mass Mn=55: O=16) Substance Manganese oxide 1. ElementsMnO 2. Mass of each element (g) 3. Mass / Atomic Mass 4. Ratio 5. Formula 5.5 3.2 5.5/55 =0.10 3.2/16 =0.20 1:2 MnO 2 Working out the formula from masses that have reacted

3.  We found 3.2g of copper reacted with 0.8g of oxygen. What is the formula of the oxide of copper that was formed? (At. Mass Cu=64: O=16) Substance Copper oxide 1. ElementsCuO 2. Mass of each element (g) 3. Mass / Atomic Mass 4. Ratio 5. Formula 3.2 0.8 3.2/64 =0.05 0.8/16 =0.05 1:1 CuO

4.  A chloride of silicon was found to have the following % composition by mass: Silicon 16.5%: Chlorine 83.5% (Atomic. Mass Si=28: Cl=35.5) Substance Silicon Chloride 1. ElementsSiCl 2. Mass of each element (g per 100g) 3. Mass / Atomic Mass 4. Ratio 5. Formula 16.5 83.5 16.5/28 =0.59 83.5/35.5 =2.35 Cl ÷Si = (2.35 ÷ 0.59) = (3.98) Ratio of Cl :Si =4:1 SiCl 4 Divide biggest by smallest Activity

5.  Calculate the formula of the compounds formed when the following masses of elements react completely: (Atomic. Mass Si=28: Cl=35.5) Element 1 Element 2 Atomic Masses Formula Fe = 5.6gCl=106.5gFe=56 Cl=35.5 K = 0.78gBr=1.6gK=39: Br=80 P=1.55gCl=8.8gP=31: Cl=35.5 C=0.6gH=0.2gC=12: H=1 Mg=4.8gO=3.2gMg=24: O=16 FeCl 3 KBr PCl 5 CH 4 MgO Activity