We also know, according to the law of conservation of mass, that all the carbon in CxHyOz had to go to CO2 and all the hydrogen in CxHyOz had to go to H2O. Now, what to do with that knowledge!!! Tip: if they give you measurements that go out to 1/1000 place—make sure to NOT do much preliminary rounding! Let’s start with determining how much carbon is in the CO2: Next, how much hydrogen in water: We get the oxygen, by what is left in compound: 3.489-(2.136 + .2136) =1.139 g Oxygen 2.136 g C 0.2136 g H 1.139 g O An industrial method to produce elemental zinc from its ore is to “roast” the crude ore in oxygen and then react the oxide with CO. the following reactions describe the chemical process: (aside-- what else could we call this first reaction?) Step 1: 2ZnS + 3O2 → 2ZnO + 2SO2 Step 2: ZnO + CO → Zn + CO2 Na2CO3 . nH2O → Na2O + CO2 + nH2O. A student heats 3.9727 grams of the hydrate and collects 0.6039 grams of CO2. what is the amount of water in the original sample We cannot approach this the way we have in previous examples. AP exam is absolutely the best at taking a problem you are familiar with and approaching it from a slightly different angle. How do you know it is a new angle? Well, when you try old ways -- they don’t work! What we know: From BCE 1 mole hydrate will decompose to form 1 mole of CO2. So, let’s determine how many moles of CO2 we have.
We also know, according to the law of conservation of mass, that all the carbon in CxHyOz had to go to CO2 and all the hydrogen in CxHyOz had to go to H2O. Now, what to do with that knowledge!!! Tip: if they give you measurements that go out to 1/1000 place—make sure to NOT do much preliminary rounding! Let’s start with determining how much carbon is in the CO2: Next, how much hydrogen in water: We get the oxygen, by what is left in compound: 3.489-(2.136 + .2136) =1.139 g Oxygen 2.136 g C 0.2136 g H 1.139 g O An industrial method to produce elemental zinc from its ore is to “roast” the crude ore in oxygen and then react the oxide with CO. the following reactions describe the chemical process: (aside-- what else could we call this first reaction?) Step 1: 2ZnS + 3O2 → 2ZnO + 2SO2 Step 2: ZnO + CO → Zn + CO2 Na2CO3 . nH2O → Na2O + CO2 + nH2O. A student heats 3.9727 grams of the hydrate and collects 0.6039 grams of CO2. what is the amount of water in the original sample We cannot approach this the way we have in previous examples. AP exam is absolutely the best at taking a problem you are familiar with and approaching it from a slightly different angle. How do you know it is a new angle? Well, when you try old ways -- they don’t work! What we know: From BCE 1 mole hydrate will decompose to form 1 mole of CO2. So, let’s determine how many moles of CO2 we have.
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