UNAM 2024 CHEMISTRY Simulator Exam Higher Level with FREE PDF Answers

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Reduction is a process that involves gain of electrons, decrease in oxidation number and gain of hydrogen.

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To measure the pH scale, indicators are used that change color according to the pH of the substance and whether it is acidic, base or its pH is neutral. It is important to know the characteristic colors of both a base and an acid.

Likewise, to know the type of solution that is presented, we can know the elements of the compound, that is, whether it is composed of an acid or a base, or both.

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Catalysts are substances that increase the speed of a chemical reaction without participating in it, that is, the catalyst is recovered at the end of the reaction. A catalyst increases the rate of a chemical reaction because it decreases the activation energy.

Activation energy is the minimum amount of energy needed to start a chemical reaction.

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Remember that lipids are responsible for the storage or reserve of energy through fats.

We suggest you prepare a comparative table on the characteristics of lipids, proteins, carbohydrates and nucleic acids.

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B) Ethanal does not participate in the formation of esters through the condensation reaction, but ethanol does.

C) If these substances were used in a condensation reaction, ethyl butanoate would be formed.

D) Neither ethane nor butyl participate in condensation reactions to form esters.

We suggest you investigate the condensation and hydrolysis reaction, and consult examples that allow you to better understand the topic.

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A) Ethanol is the molecule with the highest boiling point due to its OH group, which allows hydrogen bonds to form between molecules with relatively strong bonds, hence the substance requires greater energy to convert it into a gaseous substance. The carbonyl of the aldehyde does not form such strong interactions between molecules, therefore, it does not exceed the boiling temperature of ethanol.

B) Ethane has a boiling temperature of –89 °C since it is a non-polar molecule and the interactions between molecules are very weak. At room temperature it is in a gaseous state, so, compared to ethanol, this alkane has no a boiling temperature higher than alcohol, which is 78 °C

C) Ethane has a boiling temperature of –89 °C since it is a non-polar molecule and its interactions between molecules are very weak at room temperature. It is in a gaseous state, therefore, it cannot be the molecule with the highest boiling temperature. boiling of the compounds.

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Sucrose is about six times sweeter than lactose, slightly sweeter than glucose, but only half as sweet as fructose.

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A) These processes involve enzymes that improve the quality of food, but not necessarily its use.

B) Although these processes involve enzymes, they are not directly related to the use of food.

C) These processes are fundamental in plants or autotrophic organisms, they are not directly related to the use of food.

We suggest you carry out a search on the functions of enzymes.

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Indicators are generally weak organic acids or bases, whose base or conjugate acid have different colors due to differences in their absorption spectra.

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Remember that to name an organic compound you must follow the following steps:

1) Learn the names of the so-called alkyl radicals.

2) Learn the names and identification of the simplest functional groups.

3) Combine the functional group with the nomenclature of the corresponding alkaline radical in the name of the compound.

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The oxidation order corresponds to the greatest number of bonded oxygens, as well as the greatest oxidation number of the carbon of the functional group.

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Remember that the nitrogen process is as follows:

Atmospheric nitrogen.
2. Entry into the food chain.
3. Decomposition of animal waste.
4. Return to the atmosphere due to denitrification.
5. Entry into the aquatic environment through leaching.
6. Humus.
7. Nitrification.
8. Nitrogen fixation in the roots by symbiotic bacteria.
9. Absorption of nitrogen produced by the electrical activity of the atmosphere.
10. Decomposition of plant matter.

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The electrons that participate in chemical bonds are called valence electrons and are defined as those that reside in the outer (generally incomplete) level of atoms.

The Lewis configuration for an element consists of writing the element's chemical symbol (representing the nucleus and inner electrons of the atom) plus one dot for each valence electron. Electrons are placed on all four sides of the atomic symbol.

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To increase the speed of a chemical reaction it is necessary to increase the number of collisions between the molecules and this is achieved in two ways: by increasing the temperature, which is related to the kinetic energy of the particles, and by increasing the concentration of the reactants, since that increasing the number of molecules leads to a greater number of collisions between them.

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A) Ethanal is a water-soluble substance because it has the carbonyl group (–C=O), but it is not as soluble as carboxylic acid, because in addition to the carbonyl group it has the hydroxyl group (OH).

B) Ethane is a non-polar covalent molecule, which makes it a substance insoluble in water.

C) Dimethyl ether is a non-polar covalent molecule, and is insoluble in water. Despite having an oxygen atom, its position makes it non-polar, which is why it is difficult to dissociate.

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The octet rule says that the ions of elements have the tendency to complete their last energy levels with a quantity of eight electrons, in such a way that they acquire a stable configuration.

If you review this example, you will notice that C only has four electrons, so the configuration is not stable.

We suggest you verify that all the elements complete the eight electrons.

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Fecal matter, as well as detergents, are sources of water pollution generated by the constant growth of urban areas.

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Remember that the solvent is a substance that dilutes the solute, so it is found in greater quantity than the latter.

The solute is diluted in the solvent to form a solution.

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A) Colloids are heterogeneous mixtures formed by solid particles that, due to their size, are dispersed in a liquid or gas phase.

B) Suspensions are formed by insoluble solids in a liquid, unlike a colloid, the size of the solid particles is larger.

D) Emulsions are heterogeneous mixtures formed from two mutually immiscible liquids, generally mixtures of water and oil, for example, mayonnaise.

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The values ​​of n can be any positive integer, starting with n = 1 (remember that the value of n coincides with the period of the group to which the element belongs in the periodic table).

For each value of n, 2n can be accommodated² electrons. If n = 3

2 (3)² = 18

Level 3 will have the capacity to hold a maximum of 18 electrons.

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A) Lipids do not dissolve in body fat.

B) Lipids are not polar molecules that dissolve easily in water.

D) Lipids are not the union between monomers to form macromolecules.

We suggest you investigate the characteristics of lipids.

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B) Hydrocarbon chains that have unpaired electrons in an organic molecule are known as radicals.

C) and D) A functional group contains oxygen, hydrogen and nitrogen atoms that are bonded to carbon in a specific way and are responsible for the chemical behavior of the molecule. A radical is a part of the molecule that has free electrons attached to a hydrocarbon chain.

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Alkali metals do not act as oxidants, remember that when they react with water they form hydroxides, they are soft metals, with low density and the most chemically reactive, they are not found in a free state in nature, but in the form of compounds, generally salts. Additionally, they form ionic substances with non-metals.

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A) Bases do not release protons when dissolving in water.

C) The bases do not have pH values ​​less than 7.

D) Bases do not release protons when dissolving in water.

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We suggest you carry out the following procedure.

In the table we see that the compound has a continuity of going up one unit: I, II, III and IV.

The table shows that one unit of the compound has 80 g of atomic molar mass, and that this is multiplied by 2 as the units go up, that is, the compound.

1 80 x = 80
2 80 x = 160
3 80 x = 240
4 80 x = 320

Therefore, the most probable molar mass of X is 80 g/mol

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These elements do not share the same period.

A) Fluorine and nitrogen are located in period 2, but phosphorus is located in period 3.

C) Potassium and calcium are located in period 4, but antimony is located in period 5.

D) Copper is located in period 4, silver is located in period 5, and gold is located in period 6.

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A) In an elimination reaction, exactly the opposite happens, a molecule is divided into two simpler products.

C) In a substitution reaction, one atom or group of atoms in a molecule is replaced by another atom or group of atoms.

D) A condensation reaction is one in which the interaction of two molecules occurs to form a more complex product, usually with the loss of a small molecule.

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A) The carboxylic acid (I) could work, but the aldehyde (II) does not.

B) Alcohol (III) can participate, but alkyl halide (IV) cannot.

D) Neither of the two substances could participate in the formation of an ester group.

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The peptide bond occurs through a condensation reaction that is carried out with an amino group of one amino acid and with a carboxylic group of another amino acid, generating an amide and water.

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1 mole is the quantity that corresponds to 6.022 x 10²³ whether particles, atoms or molecules. In 6.022 mole you would have 36.264 x 10²³ of O molecules².

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A) Remember that Julius Meyer did not propose the arrangement of elements based on a property that he called atomic number through the X-ray spectra of various elements.

B) Remember that Johann Döbereiner did not propose the arrangement of elements based on a property that he called atomic number through the X-ray spectra of various elements.

C) Remember that John Newlands did not propose the arrangement of elements based on a property he called atomic number through the X-ray spectra of various elements.

We suggest you study the historical context in which the periodic table originated and the contributions of various scientists.

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In oxidation–reduction reactions, one chemical species is oxidized and another is reduced.