Free HESI A2 Chemistry practice for HESI A2 Chemistry Questions (HESI A2). Answer 37 nursing exam-style questions with rationales, exam mode, and progress track
Which of the following best describes an endothermic reaction?
Select the best answer.
Explanation:
An endothermic reaction is a process that absorbs heat from its surroundings. When a reaction absorbs heat, it leads to a decrease in the temperature of the surroundings, making choice A the correct description. In an endothermic reaction, energy is taken in from the surroundings, resulting in a decrease in temperature around the reaction site. Choice B is incorrect because a reaction that releases heat is known as an exothermic reaction. Choice C is incorrect as all reactions involve heat to some extent. Choice D is incorrect as an endothermic reaction does not remain at a constant temperature but rather absorbs heat, leading to a temperature decrease in the surroundings.
What is the pH of acids?
Select the best answer.
Explanation:
The correct answer is B: < 7. Acids have a pH lower than 7, indicating higher acidity. A pH below 7 signifies an acidic solution, with lower values indicating stronger acids. Choice A (7.5) is incorrect as it is greater than 7, which is alkaline. Choice C (> 7) is incorrect as values greater than 7 represent alkaline/basic solutions. Choice D (7) is incorrect because a pH of 7 is neutral, not acidic.
What is the correct formula for sodium nitrate?
Select the best answer.
Explanation:
The correct formula for sodium nitrate is NaNO₃. In this formula, 'Na' represents sodium, 'N' represents nitrogen, and 'O₃' represents three oxygen atoms. Sodium nitrate consists of one sodium ion (Naâº) and one nitrate ion (NO₃â»), which means the correct formula is NaNO₃. Choice A (NaNO) is incorrect as it lacks the subscript indicating the presence of three oxygen atoms. Choice B (Na NO) is incorrect as it includes a space between 'Na' and 'NO', which is not part of the standard chemical formula notation. Choice D (Na NOâ‚‚) is incorrect as it indicates a different compound with a nitrite ion (NOâ‚‚â») instead of nitrate ion.
What distinguishes one allotrope from another?
Select the best answer.
Explanation:
Allotropes are different forms of the same element that exist in the same physical state but have different structures. The arrangement of atoms is what distinguishes one allotrope from another, determining their unique properties and characteristics. Gram atomic mass (Choice B) is a constant value for a specific element and does not change between different allotropes. Physical state (Choice C) refers to whether a substance is a solid, liquid, or gas, which can be the same for different allotropes of an element. Stability (Choice D) can vary between different allotropes, but it is not what always differentiates one allotrope from another. Therefore, the correct answer is the arrangement of atoms, as it is the key factor that varies across different allotropes.
One factor that affects rates of reaction is concentration. Which of these statements about concentration is/are correct?
Select the best answer.
Explanation:
A higher concentration of reactants causes more effective collisions per unit time, leading to an increased reaction rate. This is because a higher concentration means there are more reactant molecules in a given volume, increasing the likelihood of collisions between them. With more collisions occurring, there is a greater chance of successful collisions leading to the formation of products, hence increasing the reaction rate. Choice B is incorrect as a lower concentration decreases the number of collisions, reducing the reaction rate. Choice C is incorrect as a higher concentration increases collision frequency, which typically results in a higher reaction rate. Choice D is incorrect as a higher concentration usually leads to more collisions, thus increasing the reaction rate.
How many electron pairs are shared to form a triple covalent bond?
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Explanation:
The correct answer is C. In a triple covalent bond, three pairs of electrons are shared between two atoms. This sharing results in a total of six electrons being shared, making the bond strong. Choice A (1) is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choice B (2) is incorrect as a double covalent bond consists of the sharing of two pairs of electrons. Choice D (4) is incorrect because there are only three pairs of electrons shared in a triple covalent bond, not four.
What is the pH of a neutral solution?
Select the best answer.
Explanation:
The correct answer is A: 7. A neutral solution has a pH of 7. In the pH scale, values below 7 are acidic, 7 is neutral, and values above 7 are basic. Therefore, a solution with a pH of 7 is considered neutral as it is neither acidic nor basic. Choices B, C, and D are incorrect because a pH of 0 indicates a strong acid, a pH of 14 indicates a strong base, and a pH of 4 indicates an acidic solution. None of these values represent a neutral solution.
Which of the following is defined as the number of cycles of a wave that move past a fixed observation point per second?
Select the best answer.
Explanation:
Frequency is defined as the number of cycles of a wave that pass a fixed observation point per second. It is a fundamental characteristic of a wave and is measured in Hertz (Hz). The frequency of a wave determines its pitch in the case of sound waves and its color in the case of light waves. Choice A, 'Wave,' is incorrect because a wave refers to the disturbance or oscillation that travels through a medium. Choice B, 'Wavelength,' is incorrect as it represents the distance between two corresponding points on a wave (e.g., crest to crest). Choice D, 'Wavefunction,' is not the correct answer as it is a mathematical function used in quantum mechanics to describe the behavior of particles and systems.
How are elements arranged in the periodic table?
Select the best answer.
Explanation:
Elements are arranged in the periodic table based on their chemical properties, making choice B the correct answer. The periodic table is organized so that elements with similar chemical properties are grouped together in columns, known as groups or families. This arrangement allows for the identification of trends in the behavior of elements and predicting their properties based on their position in the table. Choices A, C, and D are incorrect because the periodic table primarily focuses on the chemical properties of elements, not solely on atomic mass, physical state, or charge.
What is the oxidation state of the chlorine atom in the compound HCl?
Select the best answer.
Explanation:
In the compound HCl (hydrochloric acid), the hydrogen atom has an oxidation state of +1 based on the rules of assigning oxidation states. Since the overall compound is neutral, the oxidation state of chlorine must be -1 to balance the charge. Chlorine typically has an oxidation state of -1 in binary compounds with nonmetals, such as HCl. Therefore, the correct answer is -1. Choices A, C, and D are incorrect as the oxidation state of chlorine in HCl is -1, not +1, +2, or -2.
What type of starch is glycogen?
Select the best answer.
Explanation:
Glycogen is classified as animal starch, not plant starch. It is the storage form of glucose in animals, primarily found in the liver and muscles. Choice A (Plant starch) is incorrect because glycogen is not derived from plants. Choice C (Glucose) is incorrect as glucose is a monosaccharide and not a type of starch. Choice D (Cellulose) is incorrect as cellulose is a structural polysaccharide found in plant cell walls, not the same as glycogen.
On the periodic table, families of elements with similar properties appear in the same _________.
Select the best answer.
Explanation:
Families of elements with similar properties appear in the same column on the periodic table. Columns are also known as groups, and elements within the same group have similar chemical and physical properties due to their identical number of valence electrons. Therefore, the correct answer is 'column.' Choice A, 'row,' is incorrect because rows on the periodic table are called periods, not families or groups of elements. Choice B, 'principal energy level,' is incorrect as it refers to the energy levels of electrons around the nucleus of an atom, not the arrangement of elements with similar properties on the periodic table. Choice C, 'period,' is incorrect as periods represent horizontal rows on the periodic table, where elements do not necessarily have similar properties compared to elements in the same column.
Which material has the smallest specific heat capacity?
Select the best answer.
Explanation:
Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. Among the options provided, aluminum has the smallest specific heat capacity. This means that it requires the least amount of heat to raise its temperature compared to water, wood, and glass. Water has a high specific heat capacity, making it resistant to temperature changes, while wood and glass have higher specific heat capacities compared to aluminum.
A molecule of water contains hydrogen and oxygen in a 1:8 ratio by mass. This is a statement of _____.
Select the best answer.
Explanation:
The statement that a molecule of water contains hydrogen and oxygen in a 1:8 ratio by mass is an example of the law of constant composition. This law states that all samples of a given chemical compound have the same elemental composition. In the case of water (H2O), no matter where you obtain a sample of water, it will always be composed of hydrogen and oxygen in a 1:8 ratio by mass. The law of multiple proportions deals with compounds that can be formed by the combination of elements in different ratios. The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. The law of conservation of energy states that energy cannot be created or destroyed, only transferred or converted.
Which gas is released during photosynthesis?
Select the best answer.
Explanation:
During photosynthesis, plants utilize carbon dioxide and water to produce glucose and oxygen. Oxygen is released as a byproduct of this process, which is essential for the survival of most living organisms that depend on it for respiration. Therefore, the correct answer is oxygen. Choices A, C, and D are incorrect. Carbon dioxide is utilized in photosynthesis, nitrogen is not directly involved in the process, and helium is not a gas released during photosynthesis.
What is defined as the distance between adjacent peaks or adjacent troughs on a wave?
Select the best answer.
Explanation:
Wavelength is correctly defined as the distance between adjacent peaks or adjacent troughs on a wave. It is a crucial characteristic of waves, influencing properties such as color in light waves and pitch in sound waves. By altering the wavelength, significant changes in the wave's perception and attributes can be observed. Choice A, Frequency, refers to the number of occurrences of a repeating event per unit of time and is not related to the distance between peaks or troughs. Choice B, Wavenumber, represents the spatial frequency of a wave in terms of cycles per unit distance, not the distance between adjacent peaks. Choice C, Wave oscillation, does not specifically define the distance between adjacent peaks or troughs but rather the movement of a wave back and forth.
The three important allotropic forms of phosphorus are red, white, and ___________.
Select the best answer.
Explanation:
The three important allotropic forms of phosphorus are red, white, and black. These forms indicate the different physical properties and reactivity of phosphorus under various conditions. Red phosphorus is more stable and less reactive than white phosphorus, while black phosphorus is the least reactive form. Choice C, 'black,' is the correct answer as it completes the sequence of allotropic forms of phosphorus. Choices A, 'green,' B, 'gray,' and D, 'silver,' are incorrect as they do not represent recognized forms of phosphorus.
Radioactive isotopes are frequently used in medicine. What kind of half-life would a medical isotope probably have?
Select the best answer.
Explanation:
Medical isotopes used in diagnosis and treatment need to have a relatively short half-life to minimize radiation exposure to patients. If the half-life were too long (such as many years) or even years-long, the radiation would persist for too long and could be harmful to the patient. Seconds-long half-lives would not provide enough time for the isotope to be effective. Days-long half-lives strike a balance between providing enough time for the isotope to be used effectively and minimizing radiation exposure.
Which of these intermolecular forces might represent attraction between atoms of a noble gas?
Select the best answer.
Explanation:
Noble gases are non-polar molecules without a permanent dipole moment. The only intermolecular force applicable to noble gases is the London dispersion force, also known as Van der Waals forces. This force is a temporary attractive force resulting from the formation of temporary dipoles in non-polar molecules. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding involve significant dipoles or hydrogen atoms bonded to electronegative atoms, which do not apply to noble gases.
Which element has the highest electronegativity?
Select the best answer.
Explanation:
Fluorine has the highest electronegativity among the elements listed. Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Fluorine, being the most electronegative element on the periodic table, has the strongest ability to attract electrons towards itself compared to chlorine, nitrogen, and oxygen. Therefore, fluorine is the correct answer. Chlorine, nitrogen, and oxygen have lower electronegativities compared to fluorine, making them incorrect choices for the element with the highest electronegativity.
What charge do Group IA elements have?
Select the best answer.
Explanation:
Group IA elements, also known as alkali metals, have a +1 charge. They readily lose one electron to achieve a stable electron configuration, forming ions with a single positive charge. This makes +1 the correct choice. Choices B, C, and D are incorrect because alkali metals in Group IA typically lose one electron, so they do not have a +2, +3, or 0 charge.
What creates a dipole in a covalent bond?
Select the best answer.
Explanation:
A dipole is created in a covalent bond when there is an unequal sharing of electrons between the atoms involved. This results in a partial positive charge on one atom and a partial negative charge on the other, leading to a separation of charges and the formation of a dipole. Choices B, C, and D are incorrect because a dipole is specifically formed due to unequal sharing of electrons, not equal sharing, exchange, or transfer of electrons in a covalent bond.
Which element has an atomic mass greater than that of sodium?
Select the best answer.
Explanation:
Silicon has an atomic mass greater than that of sodium. The atomic mass of silicon is approximately 28.0855 u, whereas the atomic mass of sodium is approximately 22.9898 u. Therefore, silicon has a greater atomic mass compared to sodium. Boron, Oxygen, and Fluorine have atomic masses lower than sodium, making them incorrect choices in this context.
What is the primary function of enzymes?
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Explanation:
Enzymes function to speed up reactions by lowering the activation energy required for the reaction to occur. They act as biological catalysts, providing an alternative pathway for the reaction to proceed more rapidly without being consumed in the process. Choices A, C, and D are incorrect because enzymes do not provide energy for reactions (they do not generate energy), their primary function is not to decrease activation energy (though they do lower it), and while they act as catalysts, the primary function is to speed up reactions by lowering activation energy.
Which of the following elements is the most electronegative?
Select the best answer.
Explanation:
Fluorine is the most electronegative element on the periodic table. It has the highest electronegativity value, indicating its strong ability to attract electrons in a chemical bond. This property makes it highly reactive, explaining why it is the correct answer in this question. Oxygen and Nitrogen are also electronegative elements, but they are not as electronegative as Fluorine. Sodium, on the other hand, is not electronegative; it is an electropositive element.
What charge do Group IIIA elements have?
Select the best answer.
Explanation:
Group IIIA elements, also known as Group 13 elements, have a common oxidation state of +3. This is because they have three valence electrons and tend to lose these electrons to achieve a stable electron configuration, resulting in a +3 charge. Choice A (+1) and Choice B (+2) are incorrect because Group IIIA elements typically lose all three valence electrons to attain a stable configuration, leading to a +3 charge. Choice D (0) is incorrect as these elements do not gain electrons but rather lose them, resulting in a positive charge.
How many neutrons does carbon-14 have?
Select the best answer.
Explanation:
The correct answer is B: 8. Carbon-14 is an isotope of carbon with 6 protons and 8 neutrons. To determine the number of neutrons in an atom, subtract the atomic number (number of protons) from the mass number. In this case, the mass number of carbon-14 is 14, and the atomic number of carbon is 6. Therefore, 14 (mass number) - 6 (atomic number) = 8 neutrons. Choices A, C, and D are incorrect because they do not reflect the correct number of neutrons in a carbon-14 atom.
Which of the following types of matter changes in volume with changes in temperature and pressure?
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Explanation:
A gas changes its volume with changes in temperature and pressure due to the particles moving more rapidly at higher temperatures, and pressure affects the space between particles. Liquids have a relatively fixed volume but take the shape of their container. Solids have a definite shape and volume, so they do not change volume with changes in temperature and pressure. Plasma is a state of matter where particles are highly energized and do not have a fixed volume, but it does not exhibit volume changes with temperature and pressure variations.
How can the reaction rate of a chemical reaction be increased?
Select the best answer.
Explanation:
To increase the reaction rate of a chemical reaction, one effective method is to increase the temperature. Raising the temperature provides more energy to the reacting particles, enabling them to collide more frequently and with higher energy, leading to an increase in the reaction rate. While increasing the surface area, concentration of reactants, and adding a catalyst are strategies that can also enhance the reaction rate, raising the temperature has the most direct and immediate impact. Increasing the surface area allows for more contact between reactants, increasing the concentration provides more reactant particles to collide, and adding a catalyst lowers the activation energy required for the reaction to occur. However, these methods may not have as immediate and significant an effect as increasing the temperature.
Which element has the highest atomic number?
Select the best answer.
Explanation:
The correct answer is Uranium. The atomic number represents the number of protons in an atom's nucleus. Among the options provided, Uranium has the highest atomic number, which is 92. Hydrogen has an atomic number of 1, Radon has an atomic number of 86, and Bismuth has an atomic number of 83. Therefore, Uranium is the element with the highest atomic number in the given choices.
What is the normal body temperature in °C?
Select the best answer.
Explanation:
The normal body temperature for humans is 37°C. This temperature is considered average and is a standard reference point for assessing an individual's health status. It is essential for the body to maintain this temperature to ensure optimal functioning of various physiological processes. Choice A (36°C) is incorrect as it is slightly below the normal body temperature. Choice C (35°C) is also incorrect as it is significantly lower than the normal body temperature. Choice D (40°C) is incorrect as it is significantly higher than the normal body temperature and would indicate a fever or other health issue.
To the nearest whole number, what is the mass of one mole of sodium chloride?
Select the best answer.
Explanation:
The molar mass of sodium chloride (NaCl) is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl). The atomic mass of sodium is approximately 23 g/mol and chlorine is approximately 35.5 g/mol. Adding these two atomic masses gives us a molar mass of approximately 58 g/mol for sodium chloride (NaCl). Therefore, the correct answer is C, 58 g/mol. Choice A (36 g/mol) is incorrect as it does not account for the individual atomic masses of sodium and chlorine. Choice B (43 g/mol) and choice D (72 g/mol) are also incorrect as they do not reflect the accurate molar mass of sodium chloride.
What is an alloy in which another metal is dissolved in mercury (Hg) called?
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Explanation:
An amalgam is a type of alloy where another metal is dissolved in mercury (Hg). This process forms a unique mixture that has various applications in dentistry, chemistry, and other fields. Electrum is a natural alloy of gold and silver, solder is a metal alloy used to join other metals together, and bronze is a copper-tin alloy. Therefore, the correct answer is B - Amalgam.
Which of the following can act as a catalyst in a chemical reaction?
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Explanation:
Enzymes are biological catalysts that speed up chemical reactions without being consumed. They lower the activation energy required for the reaction to occur, facilitating and accelerating the process. Choice B, Light, is not a catalyst but can sometimes trigger reactions by providing energy. Choice C, Water, and choice D, Metal, are not catalysts but can participate in reactions as reactants.
Which factor does not affect the reaction rate of a chemical reaction?
Select the best answer.
Explanation:
The color of reactants is not a factor that affects the rate of a chemical reaction. Temperature, surface area, and concentration of reactants are known factors that influence the reaction rate. Temperature plays a significant role in altering the reaction rate by affecting the kinetic energy of molecules. Surface area impacts the rate by providing more area for collisions to occur. Concentration affects the frequency of effective collisions. On the other hand, the color of reactants is a physical property that does not directly affect the speed of a chemical reaction.
Among the following elements, which is a nonmetal?
Select the best answer.
Explanation:
Sulfur is a nonmetal as it is located on the right side of the periodic table. Nonmetals generally exhibit properties such as being brittle, poor conductors of heat and electricity, and having lower melting points compared to metals. Mercury (A), Magnesium (B), and Potassium (D) are all metals due to their metallic properties. Mercury is a liquid metal at room temperature, Magnesium is a solid metal, and Potassium is a solid metal as well. Therefore, the correct answer is C, Sulfur.
What is the correct formula for silver hydroxide?
Select the best answer.
Explanation:
The correct formula for silver hydroxide is AgOH. Silver hydroxide is formed by the combination of the silver ion (Agâº) with the hydroxide ion (OHâ») to create AgOH. It is essential to note that the hydroxide ion consists of one oxygen and one hydrogen atom, thus the formula AgOH. Choices A, C, and D are incorrect as they do not accurately represent the composition of silver hydroxide.
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