O lvl chem mole qns
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please try to explain as simply as possible ok? And if can,step by step! lol :D
1) A 6g of sample of pure pure carbon is completely burned in oxygen.
C + O2 > CO2
Which mass of carbon dioxide is produced?
A) 12g B)22g C)38g D)44g
2)Which volume of sulphur dioxide ( at r.t.p) is formed when 9.7g of zinc sulphide is heated in air?
2ZnS + 3O2 > 2ZnO + 2SO2
A)1.2dm^3 B)2.4dm^3 C)3.6dm^3 D)4.8dm^3
3) Propane burns completely in oxygen as shown in the equation.
C3H8 (g) + 5O2 (g) > 3CO2 (g) + 4H2O (l)
If 0.1 mol of propane is burnt completey,which volume of gaseous product is obtained,measured at room temperature and pressure?
A)0.1dm^3 B)0.3dm^3 C)2.4dm^3 D)7.2dm^3
4) What is the maximum mass of chromium, Cr, that can be extracted from 76g of chromium (III) oxide, Cr2O3?
A) 48g B)52g C)104g D)152g
pleaseeeeeeeee help! Thanks in advance :D
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Originally posted by Maith:
please try to explain as simply as possible ok? And if can,step by step! lol :D
1) A 6g of sample of pure pure carbon is completely burned in oxygen.
C + O2 > CO2
Which mass of carbon dioxide is produced?
A) 12g B)22g C)38g D)44g
No. of moles of C = 6/12 = 0.5 mole
according to the equation, 1 mole of C will produce 1 mole of CO2
Hence 0.5 mol C produce 0.5 mol CO2.
Mass of CO2 = 0.5 x Mr = 0.5 x (12 + 32) = 22
ans is B
2)Which volume of sulphur dioxide ( at r.t.p) is formed when 9.7g of zinc sulphide is heated in air?
2ZnS + 3O2 > 2ZnO + 2SO2
A)1.2dm^3 B)2.4dm^3 C)3.6dm^3 D)4.8dm^3
No. of moles of ZnS = 9.7 / Mr of ZnS = 9.7/46 = 0.1 mol
According to the equation, 2 mol ZnS produces 2 mol SO2.
Hence 0.1 mol ZnS produces 0.1 mol SO2.
Vol. of SO2 = 0.1 x 24dm3 = 2.4dm3 ans is B
3) Propane burns completely in oxygen as shown in the equation.
C3H8 (g) + 5O2 (g) > 3CO2 (g) + 4H2O (l)
If 0.1 mol of propane is burnt completey,which volume of gaseous product is obtained,measured at room temperature and pressure?
A)0.1dm^3 B)0.3dm^3 C)2.4dm^3 D)7.2dm^3
0.1 mol propane produces 0.3 mol CO2.
Volume of gas = 0.3 x 24 dm3 = 7.2dm3 Ans is D
4) What is the maximum mass of chromium, Cr, that can be extracted from 76g of chromium (III) oxide, Cr2O3?
A) 48g B)52g C)104g D)152g
No. of moles of Cr2O3 = 76/ Mr of Cr2O3 = 76/152 = 0.5 moles
1 Cr2O3 ===> 2 Cr + 3/2 O2 or 2 Cr2O3 ===> 4 Cr + 3 O2
1 mol of Cr2O3 will produce 2 moles Cr.
Hence 0.5 mol Cr2O3 will produce 1 mol Cr. Hence mass of Cr = 1 x 52 = 52g
Ar of Cr = 52, Mr of Cr2O3 = 152
pleaseeeeeeeee help! Thanks in advance :D
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done
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Originally posted by tinuviel07:
done
hmm for qn 4, why 1 mol of Cr2O3 will produce 2 moles of Cr?
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Originally posted by Maith:
hmm for qn 4, why 1 mol of Cr2O3 will produce 2 moles of Cr?
1 of this compound Cr2O3 will give you 2 Cr ions right..
that's why it's equivalent to saying 1 mole of Cr2O3 will give you 2 Moles Cr
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Originally posted by tinuviel07:
1 of this compound Cr2O3 will give you 2 Cr ions right..
that's why it's equivalent to saying 1 mole of Cr2O3 will give you 2 Moles Cr
oh..ok :D
got one more qn!
5) 500cm^3 of a solution of ethanedioic acid contain 45g of ethanedioic acid, ( COOH)2 . Calculate the concentration of the acid in g/dm^3 and in mol/dm^3.
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Originally posted by Maith:
oh..ok :D
got one more qn!
5) 500cm^3 of a solution of ethanedioic acid contain 45g of ethanedioic acid, ( COOH)2 . Calculate the concentration of the acid in g/dm^3 and in mol/dm^3.
500cm3 = 0.5 dm3
Conc in g/dm3 = 45/0.5 = 22.5g/dm3
No of moles = 45/ Mr of (COOH)2 = 45 / 90 = 0.5 moles
conc in mol/dm3 = 0.5/0.5 = 1 mol/dm3
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Originally posted by tinuviel07:
500cm3 = 0.5 dm3
Conc in g/dm3 = 45/0.5 = 22.5g/dm3
No of moles = 45/ Mr of (COOH)2 = 45 / 90 = 0.5 moles
conc in mol/dm3 = 0.5/0.5 = 1 mol/dm3
orrrrrrrrrhhhhhhhhhhhhh ok! ^^
6) Which mass of oxygen combines with 12g of magnesium?
a) 4g b) 8g c)16g d)32g
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Originally posted by Maith:
orrrrrrrrrhhhhhhhhhhhhh ok! ^^
6) Which mass of oxygen combines with 12g of magnesium?
a) 4g b) 8g c)16g d)32g
Formula of magnesium oxide = MgO
You need 1 mole of Mg and 0.5 mol O2 (or 1 mole O if you prefer)
No. of Mg = 12/24 = 0.5 mol
Hence no. of moles of O2 = 0.25
Mass of O2 = 0.25 x 32 = 8g. Ans is B
If you want to use O instead, no. of moles O = 0.5 mol
Mass of O = 0.5 x 16 = 8g (SAME ANS)
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wow i get it now haha..thank you! (((:
how in the world did u get so good in chem??!!! its insane
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2)Which volume of sulphur dioxide ( at r.t.p) is formed when 9.7g of zinc sulphide is heated in air?
2ZnS + 3O2 > 2ZnO + 2SO2
A)1.2dm^3 B)2.4dm^3 C)3.6dm^3 D)4.8dm^3
No. of moles of ZnS = 9.7 / Mr of ZnS = 9.7/46 = 0.1 mol
According to the equation, 2 mol ZnS produces 2 mol SO2.
Hence 0.1 mol ZnS produces 0.1 mol SO2.
Vol. of SO2 = 0.1 x 24dm3 = 2.4dm3 ans is B
shouldn't 9.7/46 = 0.2 mol?
so vol. of SO2 = 0.2 mol * 24dm³/mol = 4.8dm³
ans is D ?
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Mr of ZnS = 97.
I believe it's a careless mistake of taking proton number for Zn (30) and add it to S (16) = 46.
But the calculation is correctly done.