Free HESI A2 Chemistry practice for HESI A2 Chemistry Version 4 (HESI A2). Answer 26 nursing exam-style questions with rationales, exam mode, and progress track
The chemical equation Cr + Fe(NO₃)₂ --> Fe + Cr(NO₃)₂ is an example of which type of reaction?
Select the best answer.
Explanation:
The correct answer is A: Single replacement. In this reaction, chromium (Cr) replaces iron (Fe) in the compound Fe(NO₃)₂, resulting in the formation of Fe and Cr(NO₃)₂. Single replacement reactions involve an element and a compound, where the element replaces another element in the compound. The general form of a single replacement reaction is A + BC --> AC + B, where A is an element and BC is a compound. This type of reaction is also known as a displacement reaction, where a more reactive element displaces a less reactive element in a compound.
Where are protons held within an atom?
Select the best answer.
Explanation:
The correct answer is A: Nucleus. Protons are held in the nucleus, the central part of an atom where both protons and neutrons are located. Protons carry a positive charge and are specifically found within the nucleus. Orbitals and the electron cloud are regions where electrons are located surrounding the nucleus, not protons. Understanding the basic structure of an atom is fundamental in chemistry, where the nucleus serves as the core that contains the majority of the atom's mass and positive charge due to the presence of protons. This knowledge is crucial for grasping various chemical concepts and explaining the behavior of elements in chemical reactions.
Which subatomic particle does not contribute significantly to an atom's mass?
Select the best answer.
Explanation:
Electrons do not contribute significantly to an atom's mass. Protons and neutrons are much more massive than electrons and make up the majority of an atom's mass. Electrons have a very small mass compared to protons and neutrons, and their contribution to the total mass of an atom is considered negligible. Therefore, the correct answer is C, Electrons.
What is the density of a piece of cork with a volume of 23.5 cm³ and a mass of 5.7g?
Select the best answer.
Explanation:
Density is calculated by dividing the mass of an object by its volume. In this case, the density of the cork can be calculated by dividing 5.7g by 23.5 cm³, resulting in a density of approximately 0.243g/cm³. Therefore, choice A, 0.243g/cm³, is the correct answer as it accurately represents the density of the cork based on the provided values.
In an experiment, a student tests three unknown fluids with the following measurements: Fluid A: m=2060g, V=2000mL, Fluid B: m=672g, V=850mL, and Fluid C: m=990g, V=1100mL. Arrange the liquids in the correct order of how they would separate in a beaker from bottom to top.
Select the best answer.
Explanation:
To determine the order in which the liquids will separate in a beaker, we must consider their densities, calculated using the formula Density = Mass (m) / Volume (V). The liquid with the higher density will settle at the bottom, while the liquid with the lower density will rise to the top. For the given fluids, Fluid A has a density of 1.03 g/mL (2060 g / 2000 mL), Fluid B has a density of approximately 0.79 g/mL (672 g / 850 mL), and Fluid C has a density of approximately 0.90 g/mL (990 g / 1100 mL). Based on these calculations, the correct order of the fluids from bottom to top, according to increasing density, is Fluid B, Fluid C, and Fluid A.
What is the density of a block on your desk that acts as a paperweight? The block measures 3cm by 4cm by 6cm and has a mass of 184.32g.
Select the best answer.
Explanation:
To calculate density, you use the formula: Density = Mass/Volume. First, calculate the volume of the block by multiplying its dimensions: 3cm x 4cm x 6cm = 72 cm3. Next, divide the mass (184.32g) by the volume (72 cm3) to find the density. Density = 184.32g / 72 cm3 = 2.56 g/cm3. Therefore, the correct answer is B, with a density of 2.56 g/cm3.
What is the mass of ethyl alcohol that will exactly fill a 200.0 mL container?
Select the best answer.
Explanation:
To determine the mass of ethyl alcohol required to fill a 200.0 mL container, we apply the formula Mass = Volume x Density. Given that the volume is 200.0 mL and the density of ethyl alcohol is 0.789 g/mL, the calculation becomes Mass = 200.0 mL x 0.789 g/mL = 157.8 g. Therefore, the correct answer is A, 157.8 g, as this is the mass of ethyl alcohol needed to completely occupy the 200.0 mL container.
What volume of silver metal will weigh exactly 2500.0 g? The density of silver is 10.5 g/cm³.
Select the best answer.
Explanation:
To determine the volume of silver, we use the formula: Volume = Mass / Density. Substituting the given values, Volume = 2500.0 g / 10.5 g/cm³ = 238.1 cm³. Therefore, the correct answer is 238.1 cm³, which represents the volume of silver metal weighing precisely 2500.0 g at a density of 10.5 g/cm³.
A flask that weighs 345.8 g is filled with 225 mL of carbon tetrachloride. The weight of the flask and carbon tetrachloride is found to be 703.55 g. From this information, calculate the density of carbon tetrachloride.
Select the best answer.
Explanation:
To find the density of carbon tetrachloride, we need to use the formula Density = Mass / Volume. The mass of carbon tetrachloride can be calculated by subtracting the weight of the empty flask from the weight of the flask filled with carbon tetrachloride: Mass of carbon tetrachloride = 703.55 g - 345.8 g = 357.75 g. Now, we can calculate the density: Density = Mass / Volume = 357.75 g / 225 mL = 1.59 g/mL. Therefore, the correct answer is A, 1.59 g/mL.
What is the density of iron when 28.5g of iron shot is added to a graduated cylinder containing 45.5mL of water, causing the water level to rise to the 49.1mL mark?
Select the best answer.
Explanation:
To determine the density of iron, we use the formula: Density = Mass / Volume. The mass of the iron is given as 28.5g. The volume of water displaced by the iron is the final volume (49.1mL) minus the initial volume (45.5mL), resulting in 3.6mL. Therefore, the density of iron can be calculated by dividing the mass of iron (28.5g) by the volume of water displaced (3.6mL), giving us 7.92 g/mL. Therefore, choice B, 7.92 g/mL, is the correct answer.
What is the building block of proteins?
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Explanation:
Amino acids are the fundamental building blocks of proteins. Proteins are large biomolecules made up of one or more chains of amino acids. Each amino acid contains an amine group, a carboxylic acid group, and a side chain specific to each amino acid. When amino acids link together through peptide bonds, they form proteins. Lipids are a different type of biomolecule that includes fats, oils, and phospholipids. DNA is a nucleic acid that carries genetic information but is not directly involved in the structure of proteins. Cells are the basic structural and functional units of living organisms, not the building blocks of proteins.
What distinguishes the 20 common amino acids from each other?
Select the best answer.
Explanation:
The correct answer is C: R-group. The 20 common amino acids share a common backbone structure, but what differentiates them from each other is the side chain or R-group attached to this backbone. The R-group varies in composition and properties among the different amino acids, influencing their overall characteristics and functions. Options A and B are not the primary distinguishing factors among amino acids. Option D is incorrect as the R-group is the key feature that sets apart the 20 common amino acids, contributing to their individual identities and roles in biological processes.
Which type of bond involves sharing pairs of electrons?
Select the best answer.
Explanation:
In a covalent bond, atoms share pairs of electrons to achieve a stable electron configuration. This sharing of electrons leads to the formation of a strong bond between atoms. Ionic bonds, on the other hand, involve the transfer of electrons from one atom to another. Therefore, the correct answer is option B, Covalent, as it specifically describes the sharing of electron pairs, distinguishing it from ionic bonds where electron transfer occurs rather than electron sharing.
Which type of bond involves atoms gaining or losing electrons?
Select the best answer.
Explanation:
Ionic bonds involve the transfer of electrons between atoms, leading to one atom gaining electrons (becoming negatively charged) while the other loses electrons (becoming positively charged). This results in the formation of ions that are held together by electrostatic forces, creating an ionic bond. In a covalent bond, atoms share electrons rather than gaining or losing them, making option A, 'Ionic,' the correct answer to this question. Therefore, the correct answer is 'Ionic,' as it specifically involves gaining or losing electrons to form a bond.
What happens to an atom that has a positive charge?
Select the best answer.
Explanation:
When an atom has a positive charge, it means it has lost one or more electrons. Electrons carry a negative charge, so the loss of an electron results in the atom becoming positively charged. Therefore, the correct answer is B: Lost an electron.
What occurs to an atom with a negative charge?
Select the best answer.
Explanation:
When an atom has a negative charge, it means it has gained an electron. Electrons are negatively charged particles, so when an atom gains an electron, it becomes negatively charged. This process is known as gaining an electron to achieve stability through a full outer electron shell. Atoms gain or lose electrons to attain a stable electron configuration, typically following the octet rule. In this case, gaining an electron is the correct choice as it results in the atom having a negative charge.
Which type of RNA is used to carry the genetic code copied from DNA?
Select the best answer.
Explanation:
The correct answer is mRNA (messenger RNA). mRNA is responsible for carrying the genetic information copied from DNA in the cell nucleus to the ribosomes in the cytoplasm where protein synthesis occurs. This process is known as transcription. mRNA acts as a messenger, delivering the genetic instructions to the ribosomes for protein synthesis. In contrast, tRNA (transfer RNA) brings specific amino acids to the ribosome during translation, helping to assemble the protein chain. rRNA (ribosomal RNA) forms a structural and catalytic part of the ribosome itself, aiding in protein synthesis. Therefore, among the options provided, mRNA is the RNA type directly involved in carrying the genetic code from DNA for protein production.
Which type of reaction is most likely represented by the products CO2 + H2O: CO2 + H2O?
Select the best answer.
Explanation:
The reaction products CO2 and H2O suggest a combustion reaction. In a combustion reaction, a substance reacts with oxygen gas (O2) to produce carbon dioxide (CO2) and water (H2O) as products. The given reaction matches the characteristic products of a combustion reaction, indicating that option D, 'Combustion,' is the correct answer.
Which statement is true regarding combination reactions?
Select the best answer.
Explanation:
In a combination reaction, two or more substances combine to form a single product. This reaction type does not always involve only one reactant (choice A), an element and an ionic compound (choice B), or require oxygen gas (choice D). The true characteristic of combination reactions is that they form only one product, making choice C the correct answer.
In a double replacement reaction, which of the following occurs?
Select the best answer.
Explanation:
In a double replacement reaction, the cations and anions of two compounds switch places to form two new compounds. During this process, a gas, solid precipitate, or compound can be formed as the exchange of ions occurs. This often results in the formation of a new product that is insoluble and forms a solid precipitate, a gas that bubbles out, or a compound that remains in the solution. Therefore, choice C is correct as it accurately describes the typical outcomes of a double replacement reaction.
Arrange the following unknown fluids in the correct order of how they would separate in a beaker, listed from bottom to top, based on the given measurements.
Select the best answer.
Explanation:
To determine the order of separation in a beaker, we need to consider the densities of the fluids. Density (d) = mass (m) / volume (V). Comparing the densities of the fluids, we find: Fluid A: d = 2060g / 2000mL = 1.03 g/mL, Fluid B: d = 672g / 850mL = 0.79 g/mL, Fluid C: d = 990g / 1100mL = 0.90 g/mL. Since fluids separate in a beaker based on their densities (with the highest density sinking to the bottom), the correct order from bottom to top is B (highest density), then C, and finally A (lowest density). Therefore, the correct answer is A,C,B.
A block on your desk acts as a paperweight with measurements of 3 cm by 4 cm by 6 cm. The block has a mass of 184.32 g. What is its density?
Select the best answer.
Explanation:
Density is calculated by dividing mass by volume. To find the volume of the block, multiply its dimensions (3 cm x 4 cm x 6 cm = 72 cm³). Dividing the mass (184.32 g) by the volume (72 cm³) gives a density of 2.56 g/cm³. Therefore, the correct answer is B.
What is the mass of ethyl alcohol that exactly fills a 200.0 mL container?
Select the best answer.
Explanation:
To determine the mass of ethyl alcohol that fills a 200.0 mL container, we use the formula: Mass = Volume x Density. Given that the density of ethyl alcohol is 0.789 g/mL, multiplying the volume (200.0 mL) by the density gives us 200.0 mL x 0.789 g/mL = 157.8 g. Therefore, the correct answer is A, 157.8 g, representing the mass of ethyl alcohol that exactly fills the 200.0 mL container.
What volume of silver will weigh exactly 2500.0 g? The density of silver is 10.5 g/cm³.
Select the best answer.
Explanation:
To find the volume of silver, we use the formula: Volume = Mass / Density. Plugging in the given values, Volume = 2500.0 g / 10.5 g/cm³ = 238.1 cm³. Therefore, the correct answer is 238.1 cm³, which corresponds to option B.
What is the density of iron if 28.5g of iron is added to a graduated cylinder containing 45.5mL of water, causing the water level to rise to the 49.1mL mark?
Select the best answer.
Explanation:
To calculate density, divide mass by volume. First, determine the volume of iron added by subtracting the initial volume of water from the final volume with iron. The volume of iron is calculated as 49.1mL - 45.5mL = 3.6mL. Density of iron is then determined as the mass of iron divided by the volume of iron, which equals 28.5g / 3.6mL = 7.92 g/mL. Therefore, the correct answer is B, 7.92 g/mL.
What occurs to an atom that has a positive charge?
Select the best answer.
Explanation:
When an atom has a positive charge, it indicates that it has lost an electron. Electrons carry a negative charge, so the absence of an electron leads to a net positive charge for the atom. Gaining a proton or losing a proton would modify the atom's identity by changing its atomic number, but it would not directly result in a positive charge. Therefore, the correct response is that the atom lost an electron to acquire a positive charge.
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