Using the following balanced chemical equation 2SO2 + O2 + 2CaCO3 -> 2CaSO4 + 2C
ID: 740560 • Letter: U
Question
Using the following balanced chemical equation2SO2 + O2 + 2CaCO3 -> 2CaSO4 + 2CO2
How many moles of CaCO3 are needed to react with 1 mole of SO2?
Explanation / Answer
The first thing needed is a balanced chemical equation describing the reaction. To do this, the formulas for each of the chemicals have to be found. "Sulfur dioxide" = SO2 "Calcium carbonate" = CaCO3 "Oxygen gas" = O2 "Calcium sulfate" = CaSO4 "Carbon dioxide" = CO2 Next, the reaction states, "Sulfur dioxide (plus) Calcium carbonate (plus) Oxygen gas (equals) Calcium sulfate (plus) Carbon dioxide". In terms of chemistry this translates to : SO2 + CaCO3 + O2 -> CaSO4 + CO2 Next, the trick is to make sure there are exactly equal numbers of atoms on each side of the "->" sign. The only thing which does not balance is the Oxygen. There are 7 Oxygen atoms on the left side of the equation and only 6 on the right. Use a math trick to balance the reaction. First, rewrite the reaction as follows: SO2 + CaCO3 + O2 -> CaSO4 + CO2 + (1/2)O2 Well, there is no such thing as half a molecule of oxygen, so set things straight by multiplying everything by "2" to get whole numbers: 2SO2 + 2CaCO3 + 2O2 -> 2CaSO4 + 2CO2 + O2 Just like an actual mathematical equation, chemical equations can also be simplified using algebra as follows: 2SO2 + 2CaCO3 + 2O2 - O2 -> 2CaSO4 + 2CO2 + O2 - O2 2SO2 + 2CaCO3 + O2 -> 2CaSO4 + 2CO2 Now, there are 12 Oxygen atoms on each side of the equation. It is now balanced! The next trick is figuring out mass. Chemists use the number "mole" like engineers use "PI". What's confusing is a "mole" is never used itself. Instead, chemists rely on the fact 1 mole of atoms has a characteristic weight. For example, 1 mole of the atoms of each of the following elements has the following weight : Carbon = 12 grams = the atomic weight of Carbon Oxygen = 16 grams = the atomic weight of Oxygen Sulfur = 32 grams = the atomic weight of Sulfur Calcium = 40 grams = the atomic weight of Calcium Now, it should be no surprise that molecular weights are the sum of the atomic weights of all the atoms. Therefore: SO2 = 32 + 16*2 = 64 grams per mole of SO2 molecules CaCO3 = 40 + 12 + 16*3 = 100 grams / mole CaCO3 molecules Thus having gotten this far, answering the first question is mostly a matter of applying conversion factors: 1 ton = 2000 lbs 2.5 lb = 1 Kg 1 Kg = 1000 gms (19900 tons)*(2000 lbs/ton)*(1 kg/2.5 lb)*(1000 gm/kg)*(1 mole SO2/64 gms) = (19900 * 1000)/(2.5 * 64) = 124375 moles SO2 Now, here's how chemistry actually works in the real world! Note the molar ratios of SO2 and CaCO3 in the balanced equation. Both formulas have the number "2" in front of them. This means there is a 2 to 2 (or 1 to 1) relationship between SO2 and CaCO3. In other words for each SO2 there needs to be a CaCO3. Think hard and it will become apparent there will need to be 124375 moles of CaCO3. Just back calculate at this point to obtain however many tons this represents. The same proceedure is used to calculate the amount of Calcium sulfate generated.
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