202- If a mixture of magnesium and calcium oxides, with purities of 80\% and 60\% by mass respectively, reacts with 88 g of carbon dioxide gas, and 40\% of the carbon dioxide reacts with magnesium oxide and 30\% reacts with calcium oxide, how many grams of solid remain? What is the total mass percentage of the complete and incomplete reactions of the oxides with gas? (Assume gas does not react with solid metals.) The molar masses of the metals are: $C = 12,\ O = 16,\ Mg = 24,\ Ca = 40\ \text{g.mol}^{-1}$
$$\text{(1)}\ 46 \qquad \text{(2)}\ 65 \qquad \text{(3)}\ 78 \qquad \text{(4)}\ 87$$

203- Considering the following thermochemical reaction, which of the following statements is correct? $(H = 1,\ C = 12,\ Cl = 35/5\ \text{g.mol}^{-1})$
$$C_2H_4(g) + Cl_2(g) \rightarrow CH_2ClCH_2Cl(g),\quad \Delta H = -178\ \text{kJ}$$

• In the presence of iron(III) chloride catalyst, the reaction proceeds in the solid phase.
• The product of this reaction is a 1,2-dichloroalkane compound.
• To produce 24.75 g of product, 0.25 mol of chlorine gas is consumed.
• To release 8.9 kilojoules of heat, a total of 4.95 g of reactants are consumed.

1. [(1)] four
2. [(2)] three
3. [(3)] two
4. [(4)] one

204- To completely burn 4.6 g of liquid butane, how many liters of oxygen gas are needed at STP? How many grams of a 50\% aqueous solution of hydrogen peroxide (with the molar ratios of water and oxygen) are obtained? (Read from right to left; $H = 1,\ C = 12,\ O = 16\ \text{g.mol}^{-1}$)

1. [(1)] $81/6\ ,\ 13/44$
2. [(2)] $62/4\ ,\ 13/44$
3. [(3)] $81/6\ ,\ 16/86$
4. [(4)] $62/4\ ,\ 16/86$

Calculation Space
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205-- Considering the structural formula of the compound shown below, how many of the following statements are correct? ($\text{H}=1,\ \text{C}=12,\ \text{O}=16\ :\ \text{g.mol}^{-1}$)
[Figure: Structural formula of a cyclic compound with multiple OH groups, $\text{HOCH}_2$ and $\text{CH}_2\text{OH}$ substituents, and ether linkages in a bicyclic ring system]

• Its solubility in water is greater than its solubility in benzene.
• The number of carbon atoms in it equals the number of hydroxyl groups.
• It is a compound fused with two rings, each ring having one oxygen atom attached.
• If methyl groups replace the alkyl functional groups in it, its molar mass decreases by 16 mass units.

(1) one (2) two (3) three (4) four

206-- Considering the following reactions:
$$\text{H}_2(\text{g}) + \text{Cl}_2(\text{g}) \xrightarrow{\text{H}_2\text{O}(l)} 2\,\text{HCl}(\text{aq}), \quad \Delta H = -184.6\ \text{kJ}$$
$$\text{H}_2(\text{g}) \xrightarrow{\text{H}_2\text{O}(l)} 2\,\text{H}^+(\text{aq}), \quad \Delta H = 0$$
$$\text{HCl}(\text{aq}) \rightarrow \text{H}^+(\text{aq}) + \text{Cl}^-(\text{aq}), \quad \Delta H = -75.2\ \text{kJ}$$
Based on Hess's law, for the conversion of $\text{Cl}^-(\text{aq})$ to $\dfrac{1}{2}\text{Cl}_2(\text{g})$, how many grams is the substance and what is $\Delta H$?
(1) $-176.5$ g, (2) $-176.5$ g, (3) $+176.5$ g, (4) $+167.5$ g, $-167.5$

207-- Considering the structure of the caffeine molecule shown in the figure below, how many of the following statements are correct? ($\text{H}=1,\ \text{C}=12,\ \text{N}=14,\ \text{O}=16\ :\ \text{g.mol}^{-1}$)
[Figure: Structural formula of caffeine molecule showing a bicyclic ring system with $\text{CH}_3$ groups, nitrogen atoms, a carbonyl group, and $\text{CH}_3$ substituents]

• $0.2$ mol of it has a mass of $39.2$ grams.
• It has three amide groups and three amine groups.
• The difference in the number of $\text{C}-\text{H}$ bonds and $\text{C}-\text{N}$ bonds in its molecule is 2.
• The ratio of the lone pair electrons of the bonds to the number of non-bonding electron pairs in it is $3.75$.

(1) one (2) two (3) three (4) four

208-- In a gas-phase reaction, starting at 4 minutes, the change in concentration of substance $A$ equals $0.2$ mol per liter, and the change in concentration of substance $D$ equals $0.17$ mol per liter. If the average rate of change in concentration of substance $X$ is $0.2$ mol per liter per unit time, and in this time interval the closest to the stoichiometric coefficients in the balanced equation, from largest to smallest, to which substances does it correspond?
(1) $X,\ A$ (2) $A,\ X$ (3) $X,\ D$ (4) $D,\ A$
[Calculation Space]
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209. How many of the following statements are incorrect?

• In the structure of polymers, a carbon atom can have two double bonds.
• For participation in addition reactions, the presence of a double bond in the four-membered ring structure is necessary.
• The structural units of fiber polymers are connected to each other by carbon--carbon bonds.
• In condensation polymerization, based on the number of monomers used, a specific product is formed.

(1) four (2) three (3) two (4) one

210. Based on the following balanced reaction:
$$\mathrm{HOOC(CH_2)_4COOH + H_2N(CH_2)_6NH_2 \rightarrow H_2O + \cdots}$$
The organic product formed from how many carbon atoms, and per $29.2$ g of acid consumed, how many grams of this product are formed?
$$(\mathrm{H=1,\ C=12,\ N=14,\ O=16\ :\ g.mol^{-1}})$$
(1) $45.2$, $38$ (2) $48.8$, $38$ (3) $45.2$, $41$ (4) $48.8$, $41$

211. Regarding a non-ionic detergent, how many of the following statements are correct?
$$(\mathrm{H=1,\ C=12,\ O=16,\ Na=23,\ S=32\ :\ g.mol^{-1}})$$

• All its atoms are connected to each other by covalent bonds.
• In industry, it is produced from complex petrochemical materials.
• The oxidation number of the sulfur atom in it equals the oxidation number of the sulfur atom in hydrogen sulfide.
• It is traditionally produced in the city of Maragheh and is suitable for oily hair.
• If an alkyl group attached to the benzene ring has 10 carbon atoms, its molar mass would be 322 g/mol.

(1) two (2) three (3) four (4) five

212. Considering the figure below, how many of the following statements are correct?
[Figure: Two atomic diagrams labeled A and B. Atom A has electron configuration $7e^-$, $8e^-$, $1Ae^-$ (inner shells). Atom B has electron configuration $7e^-$, $8e^-$, $7e^-$ (inner shells). The reaction shown is: A $+$ B $\rightarrow \cdots$]

• Atom A, by gaining one electron, achieves a noble gas configuration.
• Atom B is a strong oxidizing element and has high reactivity.
• The conversion of atom A to a stable ion occurs as: $\mathrm{A^- \rightarrow A + e^-}$, is carried out.
• In the reaction of A with B, per transfer of two moles of electrons, one mole of product is formed.

(1) one (2) two (3) three (4) four
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213. At room temperature, 250 mL of barium hydroxide solution contains 427.5 milligrams of it. The pH of this solution is: and 150 mL of it reacts completely with phosphoric acid; how many milligrams of insoluble product form in water? $(H = 1,\ O = 16,\ P = 31,\ Ba = 137\ \text{g.mol}^{-1})$
(The balanced reaction equation is:) $\mathrm{Ba(OH)_2(aq) + H_3PO_4(aq) \rightarrow Ba_3(PO_4)_2(s) + H_2O(l)}$
(1) $355/5$ , $12$ (2) $355/5$ , $12/3$
(3) $255/5$ , $12$ (4) $255/5$ , $12/3$

214. The solution of which of the following compounds below turns pH paper blue, and among these compounds (with equal concentrations and equal temperatures), which compound has electrical conductivity closest to the electrical conductivity of potassium chloride solution?
Alum Methyl amine Ethanol Soda ash
(1) Alum, methyl amine (2) Alum, methyl amine
(3) methyl amine, ethanol (4) methyl amine, ethanol

215. Regarding the reaction: $\mathrm{12H_3PO_4(aq) + NO(g) \rightarrow aP_4(s) + bHNO_3(aq) + cH_2O(l)}$, after fully balancing the equation, how many of the following statements are correct?

• The ratio $c$ to $b$ equals $0.4$.
• It has several active anions in it.
• The oxidation number of the oxygen atom does not change in it.
• The stoichiometric coefficient of one of the reactants equals the stoichiometric coefficient of one of the products.
• The change in oxidation number of every oxidizing species multiplied by its coefficient equals the stoichiometric coefficient of one of the reactants.

(1) two (2) three (3) four (4) five

216. The activation energy of the reaction: $\mathrm{N_2(g) + O_2(g) \rightarrow 2NO(g)}$, without a catalyst is 381 and $-181$ kJ/mol. If a catalyst is used instead of an automobile catalytic converter, the activation energy of the reaction decreases to 280 kJ/mol. Which statement about it is correct?

1. Using a catalyst, the reaction enthalpy and energy content of the products decrease by approximately 25 percent.
2. Without a catalyst and using a catalyst, the energy content of the reactants is greater than that of the products.
3. In this reaction, the products are more stable than the reactants, and using a catalyst causes more heat to be transferred to the environment.
4. Using a catalyst, the rate of exit of oxygen from the automobile increases, because the activation energy for the conversion of reactants to products decreases.

Space for calculations
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217-- Regarding the electrochemical cell of aluminum -- manganese, which leads to energy production, which of the following statements is correct?
$$\mathrm{E^\circ(Al^{3+}/Al) = -1.66\,V,\quad E^\circ(Mn^{2+}/Mn) = -1.18\,V}$$

• In the balanced equation of its reaction, a total of 6 electrons are exchanged.
• The rate of change of ion concentrations of aluminum and manganese, during the reaction, are equal to each other.
• During the reaction, electrons move through the external circuit from anode to cathode, and the cathode is negatively charged.
• Solutions of manganese(II) sulfates and aluminum sulfates can participate in the half-reactions of cathode and anode, respectively.

(1) four (2) three (3) two (4) one

218-- Common chemistry concepts such as ``molecular mass'', ``Avogadro's number'', ``ionic solid'', ``hydrogen bond'', and ``hydrophobic'' are, from right to left, applicable to which of the following substances?

• [(1)] $\mathrm{HF,\ NaNO_3,\ SiO_2,\ CO_2}$
• [(2)] $\mathrm{H_2O,\ HCN,\ C(s,\ diamond),\ F_2}$
• [(3)] $\mathrm{C_2H_{12},\ PCl_3,\ SO_2,\ F_2}$
• [(4)] $\mathrm{C_2H_6,\ NaCl,\ C(s,\ graphite),\ CO_2}$

219-- If in a 5-liter closed flask at a certain temperature, 4 mol of hydrogen gas and 3 mol of nitrogen gas are mixed and heated, and at equilibrium 2 mol of nitrogen gas exists in the mixture, the equilibrium constant of this reaction is:
(1) $50$ (2) $100$ (3) $80.75$ (4) $40.25$

220-- Regarding the following, how many statements are correct? $(\mathrm{H=1,\ C=12\ ;\ g.mol^{-1}})$

• 73.5\% of the molecular mass of paraxylene is contributed by carbon.
• The number of carbon atoms in a molecule of paraxylene equals the number of styrene molecules.
• Acetic acid can be obtained directly from a suitable reaction of ethane.
• Methanol can be obtained by reacting $\mathrm{H_2}$ gas with $\mathrm{CO}$ gas using a suitable catalyst and at a suitable temperature.
• The monomers forming a polymer with the structural formula [Figure: polymer structural formula showing repeating ester-linked units with carbonyl groups] are one difunctional alcohol and one difunctional acid.

(1) five (2) four (3) three (4) two
[Space for calculations]

1) Experiments show that functional groups absorb electromagnetic radiation in the wavelength range of $10^5 - 10^{-3}$ nm.

2) Nitrogen gas does not react with either hydrogen or oxygen gases at room temperature.

3) White phosphorus, like hydrogen gas, burns in air and at room temperature.

4) The spectrum resulting from the interaction of matter and electromagnetic radiation is characteristic.

29. A pentagon is inscribed in a circle. Each side of this pentagon subtends an inscribed angle, and the chord corresponds to one inscribed angle. The sum of these inscribed angles is which of the following?
(1) $540°$ (2) $180°$ (3) $720°$ (4) $360°$
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34. A parabola with vertex coordinates $(-1, -1)$ passes through the point $(1, 1)$. If from the two foci that lie on the axis of symmetry perpendicular to the axis of the parabola, two lines parallel to the axis of the parabola are drawn on the directrix, a rectangle is formed. What is the diameter of the resulting rectangle?

• [(1)] $5\sqrt{2}$
• [(2)] $\sqrt{5}$
• [(3)] $3\sqrt{2}$
• [(4)] $\sqrt{3}$

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