211- Among all the compounds below, which are used as monomers? Except:

• [(1)] propene (2) cyanoethene (3) vinyl chloride (4) chloroatane

212- Considering the reactions below, which option is incorrect?
$$\text{(a)}\quad \mathrm{KNO_3(s)} \xrightarrow{\Delta} \mathrm{KNO_2(s) + O_2(g)}$$
$$\text{(b)}\quad \mathrm{CuSO_4(aq) + Fe(s) \rightarrow FeSO_4(aq) + Cu(s)}$$
$$\text{(c)}\quad \mathrm{2KClO_3(s)} \xrightarrow{\Delta} \mathrm{2KCl(s) + aX_2(g)}$$
$$\text{(d)}\quad \mathrm{2LiOH(aq) + CO_2(g) \rightarrow Li_2CO_3(aq) + H_2O(l)}$$

• [(1)] The coefficient $w$ in reaction (d) is positive.
• [(2)] Reaction (b) is a double displacement type.
• [(3)] In reaction (c), instead of $\mathrm{aX_2}$, $\mathrm{3O_2}$ should be placed.
• [(4)] In reaction (a), after balancing the equation, the sum of the molar coefficients of substances equals 5.

213- A mixture of calcium carbonate and copper(II) sulfate pentahydrate contains 20\% calcium by mass. What is the mass percent of water in the mixture?
$$(\mathrm{Cu=64,\ Ca=40,\ S=32,\ O=16,\ C=12,\ H=1:\ g.mol^{-1}})$$

• [(1)] $9$ (2) $18$
• [(3)] $13/5$ (4) $22/5$

[Space for calculations]
%% Page 39 Chemistry 120-C Page 21

214- Element M has oxidation numbers $+1$ and $+4$, and element X has oxidation numbers $-1$ and $-2$. If the atomic mass of X is twice the atomic mass of M, with which oxidation numbers of elements M and X is the mass percent of M in their compounds greater?
(1) $-1, +4$ (2) $-2, +4$ (3) $-2, +1$ (4) $-1, +1$

215- How many grams of aluminum must react with hydrochloric acid so that the gas produced, combined with 16 grams of oxygen, completes the reaction? $(Al = 27,\ O = 16\ \text{g.mol}^{-1})$
(1) $7/7$ (2) $13/5$ (3) $9$ (4) $18$

216- If the standard enthalpies of combustion of ethyne and ethane are $-1298$ and $-1409$ kJ/mol respectively, and the standard enthalpy of formation of $\text{H}_2\text{O(l)}$ is $-286\ \text{kJ.mol}^{-1}$, what is the standard enthalpy of formation of ethyne and ethane in kJ/mol?
(1) $111$ (2) $122$ (3) $175$ (4) $277$

217- Nitric acid is industrially produced from the oxidation of ammonia. The amount of heat exchanged per kJ for the production of each mole of nitric acid using the reaction: $\text{NH}_3(\text{g}) + 2\text{O}_2(\text{g}) \rightarrow \text{HNO}_3(\text{aq}) + \text{H}_2\text{O(l)}$, is how much?
1) $4\text{NH}_3(\text{g}) + 5\text{O}_2(\text{g}) \rightarrow 4\text{NO}(\text{g}) + 6\text{H}_2\text{O(l)}\ ,\ \Delta H = a\ \text{kJ}$
2) $3\text{HNO}_3(\text{aq}) + \text{NO}(\text{g}) \rightarrow 3\text{NO}_2(\text{g}) + \text{H}_2\text{O(l)}\ ,\ \Delta H = b\ \text{kJ}$
3) $4\text{NO}_2(\text{g}) \rightarrow \text{O}_2(\text{g}) + 4\text{NO}(\text{g})\ ,\ \Delta H = c\ \text{kJ}$
(1) $\dfrac{a-b-rc}{2}$ (2) $\dfrac{a+2b+rc}{2}$ (3) $\dfrac{-a+b+rc}{4}$ (4) $\dfrac{a-2b-rc}{4}$

218- $\Delta H$ of dissolving calcium chloride $(M = 111\ \text{g.mol}^{-1})$ in water is $-35\ \text{kJ.mol}^{-1}$. To dissolve 250 grams of it in water from $25^\circ\text{C}$ to $45^\circ\text{C}$, how many grams of water must be used? $(c_{\text{water}} = 4/2\ \text{J.g}^{-1}.^\circ\text{C}^{-1}$, heat absorbed by the calcium chloride solution is neglected.)
(1) $44/4$ (2) $66/6$ (3) $83/75$ (4) $149/85$

219- In a thermite reaction, if aluminum metal is used instead of zinc metal, by how many kJ will $\Delta H$ of the reaction change at STP?

Compound name	Iron(III) oxide	Aluminum oxide	Zinc oxide
Enthalpy of formation kJ.mol$^{-1}$	$-825$	$-1675$	$-3325$

(1) $135\circ$ (2) $128\circ$ (3) $71\circ$ (4) $53\circ$
%% Page 40 Chemistry 120-C Page 22

220. Which of the following statements are always correct?

• The electrical conductivity of equimolar solutions of electrolytes is equal to each other.
• The electrical conductivity of electrolyte solutions depends on the degree of ionic dissociation.
• The electrical conductivity of electrolyte solutions depends on the number of ions in the solution.
• By passing electric current through electrolyte solutions, no change occurs in their chemical composition.

(1) 1 (2) 2 (3) 3 (4) 4

221. Which of the following statements are correct?
A) In soap, the nonpolar part can form an unbranched hydrocarbon chain.
B) At constant temperature and pressure, the dissolution rate of NO gas is greater than that of $\mathrm{NH_3}$ and HCl gases.
C) By increasing pressure, the boiling point and vapor pressure of a solution increase.
D) The vapor pressure of a solution is lower than that of pure water.
(1) A, D (2) B, C (3) A, B, C (4) B, C, D

222. The dissolution of hydrogen sulfide gas at $25^\circ\mathrm{C}$: $0.34\,\mathrm{g}$ per $100\,\mathrm{g}$ of water at $(P = 1\,\mathrm{atm})$ is $500\,\mathrm{g}$ of water. Under these conditions, how many liters of solution contain $3.04\,\mathrm{g}$ of iron(II) sulfate dissolved?
$$(\mathrm{Fe} = 56,\ \mathrm{S} = 32,\ \mathrm{O} = 16,\ \mathrm{H} = 1\ :\ \mathrm{g.mol^{-1}})$$
(1) 2 (2) 2.5 (3) 3 (4) 3.5

223. Referring to the graph, by cooling $900\,\mathrm{g}$ of a saturated potassium chlorate solution from $94^\circ\mathrm{C}$ to $32^\circ\mathrm{C}$ and filtering off the solid, approximately how many grams of solute would remain in the solution?
[Figure: Solubility curves of various salts (KNO$_3$, KCl, NaCl, KClO$_3$) showing dissolved amount (g per 100 g water) vs. temperature ($^\circ$C)]
(1) 500
(2) 550
(3) 600
(4) 660
%% Page 41 Chemistry 120-C Page 23

224. In one liter of a solution containing two strong acids HBr and $\text{HBrO}_4$, the concentration of each is $0.01$ mol per liter. The reaction: $$\text{HBrO}_4(\text{aq}) + 5\text{HBr}(\text{aq}) \rightarrow 3\text{Br}_2(\text{l}) + 3\text{H}_2\text{O}(\text{l})$$ with rate law: $\text{rate} = k[\text{BrO}_4^-][\text{Br}^-][\text{H}^+]^2$, is carried out. By adding $0.09$ mol $\text{HBr}(\text{g})$ to this solution (without changing the volume), at the start of the reaction, the rate of the reaction compared to the initial state is how many times?
(1) $5 \times 1/\Delta$ (2) $211/\Delta$ (3) $3 \times 7/\Delta$ (4) $312/\Delta$

225. In the thermal decomposition of a sample of sodium hydrogen carbonate, after 10 minutes, 4.2 grams of it remain and 0.2 mol of water has formed. The rate of decomposition of sodium hydrogen carbonate is equal to the average rate, and at this same average rate, how many moles per minute does the other second reaction complete?
$(H = 1,\ C = 12,\ O = 16,\ Na = 23\ \text{g.mol}^{-1})$
(1) $75.4 \times 10^{-2}$ (2) $75.2 \times 10^{-2}$
(3) $60.2 \times 10^{-2}$ (4) $60.4 \times 10^{-2}$

226. If in a 2-liter flask with a movable piston, at a certain temperature, $\text{PCl}_5$ grams are given, then after formation of 71 grams of chlorine gas, the equilibrium: $\text{PCl}_5(\text{g}) \rightleftharpoons \text{PCl}_3(\text{g}) + \text{Cl}_2(\text{g})$, $K = 1\ \text{mol.L}^{-1}$ is established. Under these conditions and at constant volume, if the reaction goes to half, the reaction shifts in which direction and the initial amount of $\text{PCl}_5$ was how many moles?
$(\text{Cl} = 35/5\ \text{g.mol}^{-1})$
(1) forward, 2.5 (2) forward, 1.5 (3) backward, 2.5 (4) backward, 1.5

227. Considering the reactions below and their equilibrium constants, if the initial concentration of each of substances A and E in a closed container is $1\ \text{mol.L}^{-1}$, after equilibrium of Z is established, the concentration is how many mol per liter?
I) $\ \text{A}(\text{g}) + \text{E}(\text{g}) \rightleftharpoons 2\text{X}(\text{g})$, $\quad K_1 = 32$
II) $\ 2\text{X}(\text{g}) \rightleftharpoons 2\text{Z}(\text{g})$, $\quad K_2 = 2$
(1) $0/8$ (2) $1/6$
(3) $2/4$ (4) $3/2$

228. If the percent yield of the hypothetical equilibrium reaction: $\text{A}(\text{g}) + \text{D}(\text{g}) \rightleftharpoons 2\text{E}(\text{g}) + \text{G}(\text{g})$, where one mole of each reactant is placed in a one-liter closed container, at the reaction temperature is 60 percent, the equilibrium constant of this reaction is how many $\text{mol.L}^{-1}$?
(1) $1/35$ (2) $2/25$ (3) $3/6$ (4) $5/4$

Calculation Space
%% Page 42 Chemistry 120-C Page 24

229 – Which comparison about the number of acidic hydrogen atoms in molecules of 1-propanol (A), sulfuric acid (B), and salicylic acid (C) is correct?
(1) $B > C > A$ (2) $C > B > A$ (3) $A > C > B$ (4) $B > A > C$

230 – Based on the Lewis–Brønsted model, which compound has amphoteric properties in water?
(1) Glycine (2) Methyl benzoate (3) Ammonium chloride (4) Sodium acetate

231 – In the equilibrium reaction of ethanol and acetic acid in an acidic medium, approximately what percentage of the reaction products form the compound with the formula $(\text{H} = 1,\ \text{C} = 12,\ \text{O} = 16\ \text{: g.mol}^{-1})$?
(1) $70.45$ (2) $\Delta\circ$ (3) $75.25$ (4) $\Lambda\text{r}$

232 – If $0.8$ g of solid sodium hydroxide is added to $100\ \text{mL}$ of $0.1$ molar hydrochloric acid solution, what is the pH of the resulting solution and how many moles of ions are formed?
$$(\text{H} = 1,\ \text{O} = 16,\ \text{Na} = 23\ \text{: g.mol}^{-1})$$
(1) $0.01 \cdot 4$ (2) $0.02 \cdot 4$ (3) $0.01 \cdot 13$ (4) $0.02 \cdot 13$

233 – The sum of the oxidation numbers of carbon atoms in a molecule of benzoic acid equals the oxidation number of which element in the given compound?
(1) S in potassium sulfide (2) C in formaldehyde
(3) N in nitric acid (4) Cl in potassium chlorate

234 – If two iron electrodes are used in an electrolytic cell to purify municipal water, which statement is correct?
$$\text{Fe}^{3+}(\text{aq}) + 3\text{e}^- \rightleftharpoons \text{Fe(s)},\ E^\circ = -0.44\ \text{V}$$
$$\text{O}_2(\text{g}) + 4\text{H}^+(\text{aq}) + 4\text{e}^- \rightleftharpoons 2\text{H}_2\text{O(l)},\ E^\circ = +1.23\ \text{V}$$
$$2\text{H}_2\text{O(l)} + 2\text{e}^- \rightleftharpoons \text{H}_2(\text{g}) + 2\text{OH}^-(\text{aq}),\ E^\circ = -0.83\ \text{V}$$

1. [(1)] At the anode, hydrogen gas is released.
2. [(2)] The mass of gas released at both poles is equal.
3. [(3)] By passing electric current, iron(II) hydroxide is produced.
4. [(4)] The overall reaction of this cell is the reverse of the overall reaction of a concentrated sodium chloride solution.

235 – If in a fuel cell, hydrogen is used instead of the more expensive and more dangerous methane, to pass the same number of electrons from the circuit as consuming one mole of hydrogen, how many grams of methane must be consumed?
$$(\text{C} = 12,\ \text{H} = 1\ \text{: g.mol}^{-1})$$
(1) $4$ (2) $8$ (3) $16$ (4) $32$