- #1
pc2-brazil
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Salutations,
The answer obtained below doesn't match any of the options given in the enunciation.
Thank you in advance.
A sample of dolomitic limestone, containing 60% of calcium carbonate and 21% of magnesium carbonate, goes through decomposition when heated, according to the following equation:
[tex]CaCO_3_{(s)} + MgCO_3_{(s)} \rightarrow CaO_{(s)} + MgO_{(s)} + 2CO_2_{(g)}[/tex]
The mass of calcium oxide and the mass of magnesium oxide, in grams, obtained from the burning of 1 kg of limestone are, respectively:
a) 60; 21.
b) 100; 84.
c) 184; 96.
d) 336; 100.
e) 600; 210.
Molar masses:
CaCO3: 40 + 12 + 3*16 = 52 + 48 = 100 g.
MgCO3: 24,5 + 12 + 3*16 = 36,5 + 48 = 84,5 g.
CaO: 40 + 16 = 56 g.
Mass of CaCO3 and MgCO3 in 1 kg of dolomitic limestone (1000 g):
Mass of CaCO3: 60% of 1000 g = 600 g.
Mass of MgCO3: 21% of 1000 g = 210 g.
Discover what is the limiting reagent:
[tex]1 mol CaCO_3 \rightarrow 1 mol MgCO_3[/tex]
[tex]100 g \rightarrow 84,5 g[/tex]
[tex]600 g \rightarrow x[/tex]
x = 84,5 * 6 = 507 g of MgCO3 for consuming all of the CaCO3; since we only have 210 g:
MgCO3 => limiting.
Use the mass of MgCO3 to discover how many CaO will be produced:
[tex]1 mol MgCO_3 \rightarrow 1 mol CaO[/tex]
[tex]84,5 g \rightarrow 56 g[/tex]
[tex]210 g \rightarrow y[/tex]
[tex]y = \frac{210 \times 56}{84,5}[/tex]
y = 139,17 g.
But this mass is not in the answer options. According to the book, the right answer is D (336 g of CaO and 100 g of MgO). What is wrong, then?
Thank you in advance.
The answer obtained below doesn't match any of the options given in the enunciation.
Thank you in advance.
Homework Statement
A sample of dolomitic limestone, containing 60% of calcium carbonate and 21% of magnesium carbonate, goes through decomposition when heated, according to the following equation:
[tex]CaCO_3_{(s)} + MgCO_3_{(s)} \rightarrow CaO_{(s)} + MgO_{(s)} + 2CO_2_{(g)}[/tex]
The mass of calcium oxide and the mass of magnesium oxide, in grams, obtained from the burning of 1 kg of limestone are, respectively:
a) 60; 21.
b) 100; 84.
c) 184; 96.
d) 336; 100.
e) 600; 210.
Homework Equations
The Attempt at a Solution
Molar masses:
CaCO3: 40 + 12 + 3*16 = 52 + 48 = 100 g.
MgCO3: 24,5 + 12 + 3*16 = 36,5 + 48 = 84,5 g.
CaO: 40 + 16 = 56 g.
Mass of CaCO3 and MgCO3 in 1 kg of dolomitic limestone (1000 g):
Mass of CaCO3: 60% of 1000 g = 600 g.
Mass of MgCO3: 21% of 1000 g = 210 g.
Discover what is the limiting reagent:
[tex]1 mol CaCO_3 \rightarrow 1 mol MgCO_3[/tex]
[tex]100 g \rightarrow 84,5 g[/tex]
[tex]600 g \rightarrow x[/tex]
x = 84,5 * 6 = 507 g of MgCO3 for consuming all of the CaCO3; since we only have 210 g:
MgCO3 => limiting.
Use the mass of MgCO3 to discover how many CaO will be produced:
[tex]1 mol MgCO_3 \rightarrow 1 mol CaO[/tex]
[tex]84,5 g \rightarrow 56 g[/tex]
[tex]210 g \rightarrow y[/tex]
[tex]y = \frac{210 \times 56}{84,5}[/tex]
y = 139,17 g.
But this mass is not in the answer options. According to the book, the right answer is D (336 g of CaO and 100 g of MgO). What is wrong, then?
Thank you in advance.
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