Free HESI A2 Chemistry practice for HESI A2 Chemistry Version 2 (HESI A2). Answer 24 nursing exam-style questions with rationales, exam mode, and progress track
What is the name of a reaction in which electrons are transferred from one atom to another?
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Explanation:
A redox reaction, short for reduction-oxidation reaction, involves the transfer of electrons from one reactant to another. In these reactions, one substance is oxidized (loses electrons) while another is reduced (gains electrons). The term 'redox' comes from the simultaneous occurrence of reduction and oxidation reactions. Combustion reaction (choice A) involves a substance reacting with oxygen to produce heat and light, but it does not necessarily involve electron transfer. Synthesis reaction (choice B) involves the combination of two or more substances to form a new compound, with no mention of electron transfer. Double-displacement reaction (choice D) involves an exchange of ions between two compounds but does not specifically involve electron transfer between atoms. Therefore, option C, redox reaction, is the correct answer as it accurately describes the electron transfer process that occurs during such reactions.
What can be predicted by using the periodic table?
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Explanation:
The periodic table organizes elements based on their properties, such as atomic number, electron configuration, and chemical behavior. By examining an element's position on the periodic table, one can predict its properties, including its physical and chemical characteristics, reactivity, and other behaviors. This predictive ability is one of the fundamental strengths of the periodic table in understanding and working with elements. Therefore, the correct answer is A, as the periodic table allows for the prediction of the properties of each element based on its location and characteristics within the table.
What is a combustion reaction?
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Explanation:
A combustion reaction is a chemical process that involves a substance reacting with oxygen to produce heat and light. The key component in a combustion reaction is oxygen, making choice D the correct answer. Combustion reactions are typically exothermic, releasing energy in the form of heat and light, making choice A incorrect. Choices B and C describe different types of chemical reactions, not combustion reactions. Therefore, the correct answer is D.
What is the atomic number?
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Explanation:
The atomic number is the number of protons in an atom's nucleus. It uniquely identifies an element and determines its chemical properties. The number of neutrons and electrons can vary in an atom, but the number of protons remains constant for a specific element. Therefore, the correct answer is the 'Number of protons' (Choice B).
What is the term for the reactant that is fully consumed by the reaction?
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Explanation:
The correct answer is 'limiting reactant.' In a chemical reaction, the limiting reactant is the substance that is entirely consumed when the reaction proceeds. It determines the extent of the reaction and limits the amount of product that can be formed. The other choices, such as 'reducing agent,' 'reaction intermediate,' and 'reagent,' do not specifically refer to the reactant that is fully consumed in the reaction.
What characterizes bases or alkaline solutions?
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Explanation:
Bases or alkaline solutions are characterized by their ability to accept protons (hydrogen ions), making them hydrogen acceptors. When a base reacts with an acid, it accepts protons from the acid, forming water and a salt. This property distinguishes bases from acids, which donate protons. Therefore, the correct choice is A, as bases do not donate protons but instead accept them. This property allows bases to neutralize acids and regulate pH levels in solutions, making them crucial in maintaining the balance of acidity and alkalinity in various chemical systems.
What can be predicted using the periodic table?
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Explanation:
The periodic table serves as a fundamental tool in chemistry, organizing elements based on their atomic number, electron configuration, and recurring chemical properties. Through the arrangement of elements, one can predict various properties of each element. Periodic trends such as atomic radius, electronegativity, and ionization energy allow for the anticipation of element characteristics like reactivity, boiling point, and other physical and chemical properties. Hence, the correct answer is A: The properties of each of the elements can be successfully predicted using the periodic table.
Chemical reactions in living systems proceed along catabolic pathways, leading to an increase in which of the following?
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Explanation:
In catabolic pathways, complex molecules are broken down into simpler ones, releasing energy. This process increases entropy, which is a measure of disorder or randomness in a system. As molecules are broken down, they become more disordered, causing an increase in entropy. Therefore, the correct answer is 'Entropy.' Enthalpy refers to the total heat content of a system, glucose and glycogen are specific molecules and not directly related to the increase in disorder during catabolic reactions.
What is 119°K in degrees Celsius?
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Explanation:
The correct answer is 'B: -154°C.' To convert Kelvin to Celsius, you subtract 273.15 from the temperature in Kelvin. For 119°K: 119 - 273.15 = -154.15. Thus, 119°K is equal to approximately -154°C.
An element has 6 protons, 6 electrons, and 6 neutrons. What is its atomic number?
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Explanation:
The atomic number of an element is determined by the number of protons in its nucleus. Since the element in question has 6 protons, its atomic number is also 6. The number of neutrons and electrons does not impact the atomic number, which is solely based on the number of protons. Therefore, the correct answer is A: 6.
Which element has 13 protons, 13 electrons, and 14 neutrons?
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Explanation:
The element with 13 protons is Aluminum (Al), as the atomic number of an element is determined by the number of protons. The total number of protons and neutrons in an element's nucleus is known as the mass number. Given that the mystery element has 13 protons and 14 neutrons, it matches the characteristics of Aluminum, making it the correct answer.
What are buffers?
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Explanation:
Buffers are solutions that resist changes in pH by neutralizing small amounts of acids or bases that may be added to them. They help maintain a stable pH environment and are commonly used in various biological and chemical processes to prevent drastic changes in acidity or alkalinity. Buffers do not act as catalysts or inhibitors in reactions. Their main purpose is to stabilize pH levels and ensure a relatively constant pH within a system, making them essential in maintaining the proper conditions for many biological reactions and processes.
What defines the atomic number of an element?
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Explanation:
The atomic number of an element is defined by the number of protons in the nucleus of its atom. This number uniquely identifies an element and determines its chemical properties. Neutrons and electrons are also present in the atom and are essential, but the atomic number specifically refers to the number of protons. The number of neutrons is not the atomic number but contributes to the isotope of an element. The number of electrons can vary, but the number of protons remains constant for a specific element.
What does carbonic acid become within the human body?
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Explanation:
Carbonic acid, formed when carbon dioxide dissolves in water, plays a crucial role in maintaining the pH balance of the blood. It acts as a buffer to prevent drastic changes in blood pH, which is vital for the body's proper functioning. Carbonic acid does not digest food, kill viruses, or contribute to hair growth. Therefore, options A, B, and D are incorrect roles of carbonic acid within the human body, making maintaining the pH of blood (Option C) the correct answer.
What is the term for the reactant that is entirely consumed in a reaction?
Select the best answer.
Explanation:
The term for the reactant that is entirely consumed in a reaction is the limiting reactant. The limiting reactant is crucial in determining the maximum amount of product that can be formed as it is fully consumed in the reaction. The other choices, reducing agent, reaction intermediate, and reagent, do not specifically refer to the reactant that is completely consumed during the reaction process. Identifying the limiting reactant is essential for calculating the theoretical yield of a reaction and understanding the stoichiometry of the reaction.
In the chemical reaction CH₄ + 2O₂ --> CO₂ + 2H₂O, what are the reactants?
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Explanation:
The correct answer is 'A: CH₄ and O₂.' Reactants are the substances that undergo a change to form the products in a chemical reaction. In the given reaction, CH₄ (methane) and O₂ (oxygen) are the reactants, as they transform into CO₂ and 2H₂O, which are the products. Therefore, the correct answer is A.
Which compounds are the products of the reaction?
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Explanation:
The correct answer is 'B: CO₂ and H₂O.' In a combustion reaction between hydrocarbons and oxygen, the products formed are carbon dioxide (CO₂) and water (H₂O). The reaction can be summarized as hydrocarbon + oxygen --> carbon dioxide + water. Methane (CH₄) is a hydrocarbon and is not a product of the reaction. Therefore, the correct
How many hydrogen atoms are present in the reactants?
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Explanation:
To determine the number of hydrogen atoms in the reactants, we need to examine the chemical formula of the reactants. If the formula contains hydrogen atoms, we count them to find the total. In this case, the correct answer is 4 because there are 4 hydrogen atoms present in the reactants. The chemical formula in the reactants indicates the presence of 4 hydrogen atoms. It is crucial to pay close attention to the elements and their quantities in chemical reactions to ensure accurate analysis and understanding of reactants and products.
How many water molecules are present in the products?
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Explanation:
In chemical reactions, it is essential to balance the equation to determine the quantity of each molecule present in the products accurately. For this specific reaction, the balanced equation reveals that 2 water molecules are produced. When the reactants undergo the reaction, the products formed include 2 water molecules. Thus, the correct answer is A: 2.
Which of the following statements is most accurate about chemical formulas?
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Explanation:
The correct answer is 'B: 2H₂O represents two water molecules.' The chemical formula for water is H₂O, which consists of two hydrogen atoms and one oxygen atom per molecule. Therefore, when it is written as 2H₂O, it indicates two water molecules. Option B accurately represents this, making it the most accurate statement among the choices.
Which of the following substances is most dense?
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Explanation:
The correct answer is 'B: A cube weighing 6g and having a volume of 0.91cm³.' Density is calculated as mass divided by volume. For each option: A) 12g/4.6cm³ ≈ 2.61 g/cm³, B) 6g/0.91cm³ ≈ 6.59 g/cm³, C) 143g/24.3cm³ ≈ 5.88 g/cm³. Therefore, option B is the most dense with a density of approximately 6.59 g/cm³.
Will solids always sink in liquids?
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Explanation:
The statement 'solids will always sink in liquids' is not always true. Whether a solid sinks or floats in a liquid depends on the relative densities of the solid and the liquid. If the density of the solid is greater than the density of the liquid, the solid will sink. Conversely, if the density of the solid is less than the density of the liquid, the solid will float. Therefore, the correct answer is 'False, it depends on the density of the solid and liquid.'
Which of the following exhibits the most molecular interactions?
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Explanation:
The correct answer is 'Solid.' In solids, molecules are closely packed, leading to strong intermolecular forces and the highest number of molecular interactions among the given options. This close proximity results in strong attractions between molecules, creating a high number of interactions. In contrast, liquids have weaker intermolecular forces due to more freedom of movement among molecules, leading to fewer interactions compared to solids. Gases have the least molecular interactions as their molecules are widely dispersed and have minimal attraction to each other, resulting in the lowest number of interactions.
Which of the following states of matter exhibits the most molecular motion?
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Explanation:
The correct answer is 'C: Gas'. Gas exhibits the most molecular motion compared to solid and liquid states. In a gas state, molecules possess high kinetic energy, are spaced far apart, and move freely in all directions. This results in increased molecular motion compared to the more structured and restricted motion observed in solids and liquids. In solids, molecules are tightly packed and have minimal movement, while in liquids, although the molecules are more mobile than in solids, they are still more constrained compared to gases. Therefore, gas stands out as the state of matter with the highest molecular motion due to the high energy and freedom of movement of its molecules.
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