When HgO is heated, it decomposes into elemental mercury and molecular oxygen gas.
a. What is the theoretical mass of Hg obtained from 80.0g of the oxide?
b. If 60.0g of Hg is obtained from 80.0g of the oxide, what is the percent yield of the reaction?
look up molar mass of HgO
a. find mass of Hg in 80 g HgO
b. divide 60.0 g by mass from a.
To find the answers to these questions, you need to use stoichiometry, which is a method used in chemistry to determine the quantitative relationships between reactants and products in a chemical reaction.
a. The first question asks for the theoretical mass of Hg obtained from 80.0g of HgO. To answer this, we need to determine the balanced chemical equation for the reaction:
2 HgO(s) → 2 Hg(l) + O2(g)
From the equation, you can see that 2 moles of HgO will produce 2 moles of Hg. Since the molar mass of HgO is 216.59 g/mol, you can calculate the number of moles of HgO in 80.0g as follows:
80.0g HgO * (1 mol HgO / 216.59 g) = 0.3691 mol HgO
Since the reaction has a 2:2 mole ratio for HgO:Hg, you can conclude that you will obtain the same number of moles of Hg. So, the mass of Hg obtained can be calculated using the molar mass of Hg, which is 200.59 g/mol:
0.3691 mol HgO * (1 mol Hg / 1 mol HgO) * (200.59 g Hg / 1 mol Hg) = 73.99 g Hg
Therefore, the theoretical mass of Hg obtained from 80.0g of HgO is 73.99 grams.
b. The second question asks for the percent yield of the reaction, given that 60.0g of Hg is obtained from 80.0g of HgO. To calculate percent yield, you need to divide the actual yield (60.0g Hg) by the theoretical yield (73.99g Hg) and then multiply by 100%:
Percent Yield = (Actual Yield / Theoretical Yield) * 100%
Percent Yield = (60.0g / 73.99g) * 100% = 81.11%
Therefore, the percent yield of the reaction is 81.11%.