What substances are present, and what are their masses, after the reaction of 10

Question

What substances are present, and what are their masses, after the reaction of 10.00g of magnesium and 10.00g of oxygen. Please help. This topic is from law of constant composition

Explanation / Answer

First you must balance the chemical equation: 2Mg (s) + O2 (g) ---> 2MgO (s) MMMg = 24.305 MMO2 = 32.00 g/mol MMMgO = 40.305 g/mol Then, since an amount is given for the starting materials, you mustdetermine the limiting reagent for the reaction. Convert the givenamounts into moles of each substance. (10.00 g Mg)(1 mol Mg/24.305 gMg) = 0.41144 mol Mg (LimitingReagent) (10.00 g O2)(1 mol O2/32.00g O2) = 0.3125 mol O2(Excess material) The stochiometric ratio is 2:1, where twice as much Mg is needed toreact with a given amount of oxygen. The limiting reagent is theMg, so that amount is used to determine the amount of productformed. (0.41144 mol Mg)(2 mol MgO/2mol Mg)(40.305 g MgO/1mol MgO) = 16.58 gMgO

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