Chemistry Regents Exam Practice Test

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  • 1/22 Questions

    Which three groups of the Periodic Table contain the most elements classified as metalloids (semimetals)?

    • 1, 2, and 13
    • 2, 13, and 14
    • 14, 15, and 16
    • 16, 17, and 18
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About This Quiz

Prepare yourself to take this "Chemistry Regents Exam Practice Test" and check how well you score on this quiz. In chemistry, a reagent or analytical reagent is meant by a substance or compound which is added to a system to cause a chemical reaction or test if one occurs. The terms reactant and reagent are usually used interchangeably, but reactant tells a substance consumed during a chemical reaction. Let us test you now!

Chemistry Regents Exam Practice Test - Quiz

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  • 2. 

    What is the empirical formula of the compound whose molecular formula is P4O10?

    • PO

    • PO2

    • P2O5

    • P8O20

    Correct Answer
    A. P2O5
    Explanation
    The empirical formula of a compound represents the simplest whole number ratio of atoms present in the compound. In the given molecular formula P4O10, there are 4 phosphorus atoms and 10 oxygen atoms. To find the empirical formula, we need to divide the subscripts by their greatest common divisor, which in this case is 2. Dividing 4 by 2 gives us 2, and dividing 10 by 2 gives us 5.

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  • 3. 

    Atoms of elements in a group on the Periodic Table have similar chemical properties. This similarity is most closely related to the atoms.

    • Number of principal energy levels.

    • Number of valence electrons.

    • Atomic numbers.

    • Atomic masses.

    Correct Answer
    A. Number of valence electrons.
    Explanation
    Atoms of elements in a group on the Periodic Table have similar chemical properties because they have the same number of valence electrons. Valence electrons are the electrons in the outermost energy level of an atom and they are responsible for the atom's chemical behavior. Elements in the same group have the same number of valence electrons, which means they have similar reactivity and can form similar types of chemical bonds.

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  • 4. 

    A proton has approximately the same mass as...

    • A neutron.

    • An alpha particle.

    • A beta particle.

    • An electron.

    Correct Answer
    A. A neutron.
    Explanation
    A proton has approximately the same mass as a neutron. Protons and neutrons are both subatomic particles found in the nucleus of an atom. While protons carry a positive charge, neutrons have no charge. However, both particles have nearly the same mass, making them similar in terms of their weight.

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  • 5. 

    Compared to the charge and mass of a proton, an electron has...

    • The same charge and a smaller mass.

    • The same charge and the same mass.

    • An opposite charge and a smaller mass.

    • An opposite charge and the same mass.

    Correct Answer
    A. An opposite charge and a smaller mass.
    Explanation
    An electron has an opposite charge and a smaller mass compared to a proton. Protons have a positive charge, while electrons have a negative charge. Additionally, protons have a much larger mass compared to electrons.

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  • 6. 

    When alpha particles are used to bombard gold foil, most of the alpha particles pass through undeflected. This result indicates that most of the volume of a gold atom consists of _____.

    • Deuterons

    • Neutrons

    • Protons

    • Unoccupied space

    Correct Answer
    A. Unoccupied space
    Explanation
    When alpha particles are used to bombard gold foil, most of the alpha particles pass through undeflected. This suggests that most of the volume of a gold atom consists of unoccupied space. The alpha particles, which are positively charged, are able to pass through the gold foil without being deflected by any particles within the atom. If the gold atom was mostly composed of deuterons, neutrons, or protons, most of the alpha particles would have been deflected or absorbed by these particles.

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  • 7. 

    At STP (standard temperature and pressure), which substance is the best conductor of electricity?

    • Nitrogen

    • Neon

    • Sulfur

    • Silver

    Correct Answer
    A. Silver
    Explanation
     Silver is the best conductor of electricity at STP (standard temperature and pressure) because it has a high electrical conductivity. This is due to its atomic structure, which allows for the easy movement of electrons. Silver has a large number of free electrons that can move through the material, allowing electricity to flow easily. In comparison, substances like nitrogen, neon, and sulfur have lower electrical conductivities because they have fewer free electrons or their atomic structures restrict electron movement.

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  • 8. 

    What is the mass number of an atom which contains 28 protons, 28 electrons, and 34 neutrons?

    • 6

    • 28

    • 34

    • 62

    • 90

    Correct Answer
    A. 62
    Explanation
    The mass number of an atom is the sum of the number of protons and neutrons in its nucleus. In this case, the atom has 28 protons and 34 neutrons, so the mass number would be 28 + 34 = 62.

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  • 9. 

    Which symbols represent atoms that are isotopes?

    • C-14 and N-14

    • O-16 and O-18

    • Rn-222 and Ra-222

    • I-131 and I-131

    Correct Answer
    A. O-16 and O-18
    Explanation
    Isotopes are atoms of the same element that have different numbers of neutrons. In this case, O-16 and O-18 are isotopes of oxygen because they have the same number of protons (8) but different numbers of neutrons (8 and 10, respectively). C-14 and N-14 are not isotopes because they are different elements (carbon and nitrogen) and have different numbers of protons. Rn-222 and Ra-222 are also not isotopes because they are different elements (radon and radium). I-131 and I-131 are not isotopes because they have the same number of protons and neutrons, making them the same isotope.

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  • 10. 

    An ion with 5 protons, 6 neutrons, and a charge of 3+ has an atomic number of...

    • 5

    • 6

    • 8

    • 11

    Correct Answer
    A. 5
    Explanation
    An ion with 5 protons and a charge of 3+ means that it has lost 3 electrons. The atomic number of an element is determined by the number of protons in its nucleus. 

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  • 11. 

    What is the gram formula mass of K2CO3?

    • 106 g

    • 67 g

    • 99 g

    • 138 g

    Correct Answer
    A. 138 g
    Explanation
    The gram formula mass of a compound is the sum of the atomic masses of all the atoms in its formula. In the case of K2CO3, we have 2 potassium atoms (atomic mass = 39.1 g/mol), 1 carbon atom (atomic mass = 12.0 g/mol), and 3 oxygen atoms (atomic mass = 16.0 g/mol). Adding these up, we get (2 * 39.1) + 12.0 + (3 * 16.0) = 78.2 + 12.0 + 48.0 = 138.2 g. 

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  • 12. 

    Which atom contains exactly 15 protons?

    • P-32

    • S-32

    • O-15

    • N-15

    Correct Answer
    A. P-32
    Explanation
    P-32 (phosphorus) is the correct answer because the atomic number of an atom represents the number of protons it contains. Since P-32 has an atomic number of 15, it means that it contains exactly 15 protons.

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  • 13. 

    What is the total number of atoms represented in the formula CuSO4 . 5H2O?

    • 8

    • 21

    • 13

    • 27

    Correct Answer
    A. 21
    Explanation
    To determine the total number of atoms in the formula ( CuSO4. 5H2O ), let's break it down:

    ( CuSO4 ) contains:
    1 ( Cu ) atom
    1 ( S ) atom
    4 ( O ) atoms

    ( 5H2O ) contains:
    5 ( times ) 2 ( H ) atoms = 10 ( H ) atoms
    5 ( times ) 1 ( O ) atoms = 5 ( O ) atoms

    Summing up all the atoms:

    ( Cu ) = 1
    ( S ) = 1
    ( O ) = 4 + 5 = 9
    ( H ) = 10

    Adding them together: 
    1 ( Cu ) + 1 ( S ) + 9 ( O ) + 10 ( H ) = 21 atoms

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  • 14. 

    Which element has the highest first ionization energy?

    • Sodium

    • Aluminum

    • Calcium

    • Phosphorus

    Correct Answer
    A. Phosphorus
    Explanation
    Phosphorus has the highest first ionization energy among the given elements. Ionization energy refers to the energy required to remove an electron from an atom. Phosphorus has a smaller atomic radius and higher effective nuclear charge compared to the other elements. This means that the electrons in phosphorus are held more tightly by the nucleus, making it more difficult to remove an electron.

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  • 15. 

    Which element in Group 15 has the strongest metallic character?

    • Bi

    • As

    • P

    • N

    Correct Answer
    A. Bi
    Explanation
    Bi (bismuth) has the strongest metallic character among the elements in Group 15. This is because as you move down the group, the metallic character increases. Bismuth is the bottommost element in Group 15, and it has the largest atomic radius and the highest number of filled electron shells. These factors contribute to its strong metallic character, as larger atomic size allows for more delocalized electrons and better metallic bonding.

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  • 16. 

    What is the percent by mass of oxygen in magnesium oxide, MgO?

    • 20%

    • 30%

    • 40%

    • 50%

    • 60%

    Correct Answer
    A. 40%
    Explanation
    In magnesium oxide (MgO), there is one atom of magnesium (Mg) and one atom of oxygen (O). The atomic mass of magnesium is 24.31 g/mol, and the atomic mass of oxygen is 16.00 g/mol. The molar mass of MgO is the sum of the atomic masses of Mg and O, which is 40.31 g/mol. The mass of oxygen in MgO is 16.00 g/mol. To calculate the percent by mass of oxygen in MgO, divide the mass of oxygen by the molar mass of MgO and multiply by 100. Therefore, the percent by mass of oxygen in MgO is (16.00 g/mol / 40.31 g/mol) * 100 = 39.7%. Rounded to the nearest whole number, the answer is 40%.

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  • 17. 

    When a metal atom combines with a nonmetal atom, the nonmetal atom will...

    • Lose electrons and decrease in size.

    • Lose electrons and increase in size.

    • Gain electrons and decrease in size.

    • Gain electrons and increase in size.

    Correct Answer
    A. Gain electrons and increase in size.
    Explanation
    When a metal atom combines with a nonmetal atom, the metal atom tends to lose electrons and become positively charged, while the nonmetal atom tends to gain those electrons and become negatively charged. This transfer of electrons leads to the formation of an ionic bond between the two atoms. As a result, the nonmetal atom gains electrons and increases in size due to the increased electron-electron repulsion, which causes the electron cloud to expand.

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  • 18. 

    Which formula represents a molecular substance?

    • CaO

    • CO

    • Al2O3

    • Li2O

    Correct Answer
    A. CO
    Explanation
    The formula that represents a molecular substance is CO (carbon monoxide).
    CaO (calcium oxide), Al2O3 (aluminum oxide), and Li2O (lithium oxide) are all ionic compounds, as they are formed between metals and non-metals with ionic bonds.
    CO (carbon monoxide) is a molecular compound, as it is formed between two non-metals (carbon and oxygen) with a covalent bond.

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  • 19. 

    Given the unbalanced equation: Al + O2 = Al2O3 When this equation is completely balanced using the smallest whole numbers, what is the sum of the coefficients?

    • 9

    • 3

    • 4

    • 7

    Correct Answer
    A. 9
    Explanation
    The total of the coefficients in a chemical equation, which represents the number of reacting molecules and the produced products, is 9. To balance the equation, coefficients are added to the front of each element or compound as needed, ensuring an equal number of atoms or compounds on both sides of the arrow. This process involves multiplying the quantity of atoms or compounds on one side to align with the amount on the other side. In the given balanced chemical equation, the coefficients 4, 3, and 2 are associated with the reactants and products, resulting in a sum of 9.

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  • 20. 

    Which statement correctly describes the properties of sodium chloride (NaCl) when it is dissolved in water?

    • NaCl retains its crystalline structure in the solution.

    • NaCl molecules are separated into Na and Cl atoms in the solution.

    • NaCl molecules are separated into Naāŗ ions and Clā» ions in the solution.

    • NaCl increases the pH of the solution, making it more acidic.

    Correct Answer
    A. NaCl molecules are separated into Naāŗ ions and Clā» ions in the solution.
    Explanation
    Sodium chloride (NaCl) dissociates into sodium ions (Naāŗ) and chloride ions (Clā») when it dissolves in water. This process involves the separation of NaCl into its constituent ions, not atoms, facilitated by the polar nature of water molecules. The solution does not retain the crystalline structure of solid NaCl, and while NaCl's dissociation affects the solution's conductivity, it does not significantly change the pH to make it more acidic or basic; therefore, options A, B, and D are incorrect.

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  • 21. 

    Which is the correct formula for nitrogen (1) oxide?  

    • NO

    • N2O

    • NO2

    • N2O3

    Correct Answer
    A. N2O
    Explanation
    The correct formula for nitrogen (1) oxide is N2O. The notation Nv2O is used to represent N2O.

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  • 22. 

    What is the total number of moles of hydrogen gas contained in 9.03 x 1023?

    • 1.50 moles

    • 2.00 moles

    • 6.02 moles

    • 9.03 moles

    Correct Answer
    A. 1.50 moles
    Explanation
    The total number of moles of hydrogen gas contained in 9.03 x 10^23 is 1.50 moles. This can be determined by using Avogadro's number, which states that there are 6.02 x 10^23 molecules in one mole of a substance. Therefore, dividing 9.03 x 10^23 by Avogadro's number gives us the number of moles, which is approximately 1.50 moles.

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Daniel P |MSEd (Science Education) |
Science Teacher
Daniel P. is an experienced STEM club teacher with 11 years of urban teaching experience. He holds a MSEd in Science Education from The City College of New York and a BA in History from Binghamton University. He is committed to enhancing student education, using his expertise in curriculum design, differentiated instruction, and Google Classroom.

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