VASA YRKESHGSKOLA
Chemistry
Kerstin Siegfrids Stoichiometry Exercisepaper 3 Binh Bui
e1300518 I-IT-3N11. Calculate the number of grams of lead (Pb) in
12,4 moles of lead.
1 mol Pb = 207.2 g Pb (from Periodic Table)The molar mass. n =
m/M m= 207.2*12.4 = 2569.28 g Pb2. What is the mass (in grams) of
one iodine (I) atom?
Mass of 1 atom = mass of a mole of atoms / 6.022 x 1023Mass of
one iodine atom = 126.90 g / 6.022 x 1023 = 2.107 x 10-223. How
many H atoms are in 72,5 g of isopropanol (rubbing alcohol)
C3H8O?Mol of isopropanol: n = 72,5/(12*3+1*8+16*1) = 1.21 mol1 mol
C3H8O = 8 mol HMol of H = 1.21*8 = 9.68 molH atoms = 9.68 * 6,022 *
1023 = 58,3 * 1023atoms
4. Phosphoric acid H3PO4 is a colorless, syrupy liquid used in
detergents, fertilizers, toothpastes, and in carbonated beverages
for a tangy flavor. Calculate the percent composition by mass of H,
P and O in this compound.Molar mass = 3*1.008 + 30.973 + 4*15.999 =
97.993Percent Composition:%H = 3*1.008/97.993 = 3.08%%P =
30.973/97.993 = 31.6%%O = 4*15.999/97.993 = 65.31%
5. Ascorbic acid (vitamin C) cures scurvy. It is composed of
40,92 percent carbon (C), 4,58 percent hydrogen (H) and 54,5
percent oxygen (O) by mass. Determine its empirical formula.a,b,c
are the number of molecules of C, H and O respectively. We
obtain:
Therefore, we get: a = c = 6, b= 8C6H8O6
6. We have iron ore containing 23 mass% of hematite Fe2O3. How
much iron would it theoretically be possible to obtain form one ton
of this ore?
Mass Iron = 23% * 1 ton = 230 kg
7. Balance the following reactions (fill in correct
coefficients):
a) Fe2O3 + 3CO 2Fe + 3CO2
b) 3Fe+4H2OFe3O4+4H2
c) 2HNO3+FeSFe(NO3)2 +H2S
8. The food we eat is degraded, or broken down, in our bodies to
provide energy for growth and function. A general overall equation
for this very complex process represents the degradation of glucose
(C6H12O6) to carbon dioxide (CO2) and water (H2O):
C6H12O6 + 6 O2 6 CO2 + 6 H2O
If 968 g of C6H12O6 is consumed by a person over a certain
period, what is the mass of CO2 produced?
Mol of C6H12O6 = 968/(12*6 + 1*12 + 16*6) = 5.37 mol1 mol of
C6H12O6 = 6 mol CO2Mass of CO2 = 5.37 * 6 * (12+16*2) = 1.417
kg
9. It is possible to produce iron according to the following
equation:
Fe2O3 + 3 CO 2 Fe + 3 CO2
a) How many moles of iron can we get out of one mole of hematite
Fe2O3 ?2 molesb) How many moles of hematite will be needed to
produce 3 moles of carbon dioxide?1 molec) How many grams of iron
can be produced using one mole of hematite?2 * 56 = 112 gramsd) How
many grams of hematite will be required to produce 100 grams of
iron?Mols of Iron = 100/56 = 1.78 molMol of Hematite = 1.78/2 =
0.89 molMass of hematite = 0.89*(56*2 + 12*3)=131.72 grams
10. The reaction between nitric oxide (NO) and oxygen to form
nitrogen dioxide (NO2) is a key step in photochemical smog
formation:
2NO (g) + O2 (g) 2NO2 (g)
How many grams of O2 are needed to produce 2,21 g of NO2?
Mol of NO2 = 2.21/(14+16*2) = 0.05 mol2 mol NO2 = 1 mol O2Mol O2
= 0.05/2 = 0.025 molMass of O2 = 0.025 * (16*2) = 8 grams
