 |
| Chemical Reaction |
Pg 180 #1-12
1. State the law of conservation of matter:
a. In a chemical reaction, matter is neither created nor destroyed.
2. What is a scientific law?
a. Scientfic law summarizes what has been learned by careful observation of nature.
3. Why are the expressions such as “using up” and “throwing away” misleading, if the law of conservation of matter is taken into account?
a. It is misleading because in the law of conservation of matter, matter can not be used up or thrown away because matter cannot be created nor destroyed.
4. Complete atom inventories to decide if each of these chemical expressions is balanced.
a. The preparation of tin(II) fluoride, a component of some toothpastes (called stannous fluoride in some ingredient lists):
Sn(s) + HF(aq) => SnF2(aq) + H2(g)
REACTANTS | PRODUCTS |
Sn= 1 | Sn= 1 |
H= 1 | F= 2 |
F= 1 | H= 2 |
UNBALANCED
b. The synthesis of carborundum for sandpaper:
SiO2(s) + C(s) => SiC(s) + CO(g)
REACTANTS | PRODUCTS |
Si= 1 | Si= 1 |
O= 2 | C=2 |
C= 1 | O= 1 |
UNBALANCED
c. The reaction of antacid with stomach acid (hydrochloric acid):
Al(OH)3(s) + 3 HCl(aq) => AlCl3(aq) + 3 H2O(l)
REACTANTS | PRODUCTS |
Al= 1 | Al= 1 |
O= 3 | Cl=3 |
H= 6 | O= 3 |
Cl= 1 | H= 6 |
BALANCED
5. Consider this equation:
N2(g) + 3 H2(g) => 2 NH3(g)
a. What is the coefficient for the Hydrogen gas?
i. 3
b. What is the coefficient for the NH3 gas?
i. 2
c. What is the coefficient for the Nitrogen gas?
i. 1
6. For each of the following processes, draw a representation of the chemical statement, balance the representation, and verify your answer.
a. Preparing the tungsten from one of its minerals:
WO3 + 3 H2 => W + 3 H2O (1,3,1,3)
b. Heating lead(II) sulfide in air:
2 PbS + 3 O2 => 2 PbO + 2 SO2 (2,3,2,2)
c. Rusting (oxidation) of iron metal:
4 Fe + 3 O2 => 2 Fe2O3 (4, 3, 2)
7. Balance each of these chemical expressions.
a. Preparing phosphoric acid (used in making soft drinks, detergents, and other products) from calcium phosphate and sulfuric acid:
1 Ca3(PO4)2 + 3 H2SO4 => 2 H3PO4 + 3 CaSO4 (1, 3, 2, 3)
b. Completely burning gasoline:
2 C8H18 + 25 O2 => 16 CO2 + 18 H2O (2, 25, 16, 18)
8. A student is asked to balance a chemical expression:
a. Complete an atom inventory of the student’s answer. Are the atoms conserved?
REACTANTS | PRODUCTS |
Na= 2 | Na= 2 |
S= 1 | Cl= 1 |
O= 4 | K= 2 |
K= 2 | S= 1 |
Cl= 1 | O= 4 |
Yes, the atoms are conserved.
b. Did the student create a properly balanced chemical equation? Explain.
i. No, because the number of atoms that were in the products side were changed because of subscripts, not coefficients, which is the incorrect way to balance an equation.
c. If your answer to question 8b is no, write a correctly balanced equation
i. 1 Na2SO4 + 2 KCl --> 2 NaCl + 1 K2SO4 (1, 2, 2, 1)
9. If you could spend a billion dollars per second, how many years would it take to spend one mole of dollars?
a. 40 million years
10. Find the molar mass of each of the following substances:
a. Oxygen gas, O2: 32 grams
b. Ozone, O3: 48 grams
c. Limestone, CaCO3: 100 grams
d. A typical antacid, Mg(OH)2: 58 grams
e. Aspirin, C9H8O4: 180 grams
11. How can samples of 63.6 grams copper metal and 23.0 grams sodium metal, with different masses, volumes, and densities, both correctly represent 1.00 mol of substance?
a. This is because one mol is an amount that puts elements into large enough units that it can be shown in a lab. It is also used for counting, similar to a dozen.
12. A major advantage of the mole concept is that it enables a chemist to “count by weighing”. If one mole of potassium metal has a mass of 39.1 grams,
a. How many atoms are in 39.1 grams potassium?
i. 1 atom
b. How many atoms are in 19.55 grams potassium?
i. 0.5 atoms
c. How many atoms are in 3.91 grams potassium?
i. 0.1 atoms
d. How many atoms are in 1.0 grams potassium?
i. .039 atoms
No comments:
Post a Comment