C832 Chemistry with Lab
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Free C832 Chemistry with Lab Questions
1. Name the acid HNO₂.
- Nitric acid
- Nitrous acid
- Hyponitrous acid
- Pernitric acid
Explanation
Explanation:
The correct name for HNO₂ is nitrous acid. This acid contains the nitrite ion (NO₂⁻), and according to oxyacid naming rules, when the anion ends in “-ite,” the acid name ends in “-ous.” Therefore, nitrite corresponds to nitrous acid, while nitrate (NO₃⁻) would form nitric acid (HNO₃). Nitrous acid is a weak, unstable acid typically found only in aqueous solution.
Correct Answer: Nitrous acid
The correct name for HNO₂ is nitrous acid. This acid contains the nitrite ion (NO₂⁻), and according to oxyacid naming rules, when the anion ends in “-ite,” the acid name ends in “-ous.” Therefore, nitrite corresponds to nitrous acid, while nitrate (NO₃⁻) would form nitric acid (HNO₃). Nitrous acid is a weak, unstable acid typically found only in aqueous solution.
Correct Answer: Nitrous acid
2. Calculate the mass of Fe₂O₃ produced from 44.8 g of Fe
- 63.9 g
- 127.8 g
- 159.7 g
- 319.4 g
Explanation
Explanation:
The molar mass of iron (Fe) is 55.85 g/mol. 44.8 g of Fe corresponds to 44.8 ÷ 55.85 ≈ 0.802 moles of Fe. From the balanced equation, 4 moles of Fe produce 2 moles of Fe₂O₃, so 0.802 moles of Fe produce (0.802 × 2 ÷ 4) ≈ 0.401 moles of Fe₂O₃. The molar mass of Fe₂O₃ is (2×55.85 + 3×16) = 159.7 g/mol. Multiplying 0.401 moles × 159.7 g/mol ≈ 64 g, which rounds to 63.9 g of Fe₂O₃.
Correct Answer: 63.9 g
Why the other options are incorrect:
127.8 g would correspond to double the calculated moles; 159.7 g is the molar mass itself, not the yield; 319.4 g is approximately double the molar mass.
The molar mass of iron (Fe) is 55.85 g/mol. 44.8 g of Fe corresponds to 44.8 ÷ 55.85 ≈ 0.802 moles of Fe. From the balanced equation, 4 moles of Fe produce 2 moles of Fe₂O₃, so 0.802 moles of Fe produce (0.802 × 2 ÷ 4) ≈ 0.401 moles of Fe₂O₃. The molar mass of Fe₂O₃ is (2×55.85 + 3×16) = 159.7 g/mol. Multiplying 0.401 moles × 159.7 g/mol ≈ 64 g, which rounds to 63.9 g of Fe₂O₃.
Correct Answer: 63.9 g
Why the other options are incorrect:
127.8 g would correspond to double the calculated moles; 159.7 g is the molar mass itself, not the yield; 319.4 g is approximately double the molar mass.
3. Which statement regarding quantum numbers is not correct?
- Electrons may have quantum numbers that overlap as long as they are not in the same place at the same time.
- A set of quantum numbers is a representation of the location of an electron within an atom.
- There is no real significance to the values of the spin quantum number, except to distinguish electrons in the same orbital from each other.
- No two electrons within an atom can be represented by an identical set of quantum numbers.
Explanation
Explanation:
The statement “Electrons may have quantum numbers that overlap as long as they are not in the same place at the same time” is not correct. According to the Pauli Exclusion Principle, no two electrons in the same atom can have an identical set of four quantum numbers (n, l, mₗ, m ). Each electron in an atom must have a unique combination of these values, ensuring that even electrons in the same orbital differ by their spin quantum number.
Correct Answer:
Electrons may have quantum numbers that overlap as long as they are not in the same place at the same time.
The statement “Electrons may have quantum numbers that overlap as long as they are not in the same place at the same time” is not correct. According to the Pauli Exclusion Principle, no two electrons in the same atom can have an identical set of four quantum numbers (n, l, mₗ, m ). Each electron in an atom must have a unique combination of these values, ensuring that even electrons in the same orbital differ by their spin quantum number.
Correct Answer:
Electrons may have quantum numbers that overlap as long as they are not in the same place at the same time.
4. The quantum mechanical model of the atom gives up trying to specify the location of the electron and instead shows us what?
- The exact size of the electron
- The exact speed of the electron
- The probability of finding the electron
- The exact size of its orbit
Explanation
Explanation:
The quantum mechanical model of the atom is based on the principles of quantum theory, which describe electrons as existing in regions of space where they are most likely to be found rather than in fixed orbits. This model focuses on probability distributions, known as orbitals, which represent areas where there is a high likelihood of finding an electron at any given time. It abandons the classical idea of defined paths or locations, acknowledging that the exact position and momentum of an electron cannot be known simultaneously, as stated by the Heisenberg uncertainty principle.
Why the other options are incorrect:
The other options refer to exact classical properties that quantum mechanics does not specify.
The quantum mechanical model of the atom is based on the principles of quantum theory, which describe electrons as existing in regions of space where they are most likely to be found rather than in fixed orbits. This model focuses on probability distributions, known as orbitals, which represent areas where there is a high likelihood of finding an electron at any given time. It abandons the classical idea of defined paths or locations, acknowledging that the exact position and momentum of an electron cannot be known simultaneously, as stated by the Heisenberg uncertainty principle.
Why the other options are incorrect:
The other options refer to exact classical properties that quantum mechanics does not specify.
5. Balance the equation: __C₃H₈ + __O₂ → __CO₂ + __H₂O
- 1, 5, 3, 4
- 2, 10, 6, 8
- 1, 3, 3, 4
- 1, 10, 6, 8
Explanation
To balance the combustion of propane (C₃H₈), count the atoms of each element on both sides. Propane contains 3 carbon atoms and 8 hydrogen atoms. Therefore, 3 CO₂ molecules are needed to balance carbon, and 4 H₂O molecules to balance hydrogen. This results in a total of 10 oxygen atoms on the product side (6 from CO₂ and 4 from H₂O), requiring 5 O₂ molecules on the reactant side. The balanced equation is:
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.
Correct Answer: 1, 5, 3, 4
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.
Correct Answer: 1, 5, 3, 4
6. What mass of oxygen is needed to burn 32 g of CH₄ completely?
- 64 g
- 32 g
- 128 g
- 16 g
Explanation
Explanation:
The combustion reaction is CH₄ + 2 O₂ → CO₂ + 2 H₂O. One mole of CH₄ (16.0 g) requires 2 moles of O₂ (2 × 32.0 g = 64.0 g). For 32 g CH₄ you have 32 / 16 = 2.0 moles of CH₄, so you need 2.0 × 2 = 4.0 moles O₂. Mass of O₂ = 4.0 mol × 32.0 g/mol = 128.0 g.
Correct Answer: 128 g
Why the other options are incorrect:
64 g for 1 mole CH₄; 32 g is O₂ molar mass; 16 g is CH₄ molar mass.
The combustion reaction is CH₄ + 2 O₂ → CO₂ + 2 H₂O. One mole of CH₄ (16.0 g) requires 2 moles of O₂ (2 × 32.0 g = 64.0 g). For 32 g CH₄ you have 32 / 16 = 2.0 moles of CH₄, so you need 2.0 × 2 = 4.0 moles O₂. Mass of O₂ = 4.0 mol × 32.0 g/mol = 128.0 g.
Correct Answer: 128 g
Why the other options are incorrect:
64 g for 1 mole CH₄; 32 g is O₂ molar mass; 16 g is CH₄ molar mass.
7. The formula for aluminum sulfide is:
- AlS
- Al₂S₃
- Al₃S₂
- AlS₃
Explanation
Explanation:
The correct formula for aluminum sulfide is Al₂S₃. Aluminum forms a +3 ion (Al³⁺), while sulfur forms a -2 ion (S²⁻). To balance the charges, two aluminum ions (total +6) combine with three sulfur ions (total -6), forming the neutral compound Al₂S₃. This compound is an ionic solid commonly used in chemical synthesis and materials science.
Correct Answer: Al₂S₃
The correct formula for aluminum sulfide is Al₂S₃. Aluminum forms a +3 ion (Al³⁺), while sulfur forms a -2 ion (S²⁻). To balance the charges, two aluminum ions (total +6) combine with three sulfur ions (total -6), forming the neutral compound Al₂S₃. This compound is an ionic solid commonly used in chemical synthesis and materials science.
Correct Answer: Al₂S₃
8. Balance the redox equation in acidic medium: __MnO₄⁻ + __Fe²⁺ → __Mn²⁺ + Fe³⁺
- 2, 10, 2, 10
- 1, 5, 1, 5
- 5, 1, 5, 1
- 1, 8, 1, 8
Explanation
Explanation:
In acidic solution the permanganate ion (MnO₄⁻) is reduced to Mn²⁺ while Fe²⁺ is oxidized to Fe³⁺. Balancing half-reactions and then combining them gives: MnO₄⁻ + 5 Fe²⁺ + 8 H⁺ → Mn²⁺ + 5 Fe³⁺ + 4 H₂O. That corresponds to coefficients (MnO₄⁻, Fe²⁺, Mn²⁺, Fe³⁺) = (1, 5, 1, 5). The option showing multiples of that (2,10,2,10) is just a scaled version; the simplest integer set with H⁺ = 8 is 1,5,1,5 as shown.
Correct Answer: 1, 5, 1, 5
Why the other options are incorrect:
2,10,2,10 is scaled but not simplest; 5,1,5,1 reverses ratios; 1,8,1,8 confuses H⁺ coefficient.
In acidic solution the permanganate ion (MnO₄⁻) is reduced to Mn²⁺ while Fe²⁺ is oxidized to Fe³⁺. Balancing half-reactions and then combining them gives: MnO₄⁻ + 5 Fe²⁺ + 8 H⁺ → Mn²⁺ + 5 Fe³⁺ + 4 H₂O. That corresponds to coefficients (MnO₄⁻, Fe²⁺, Mn²⁺, Fe³⁺) = (1, 5, 1, 5). The option showing multiples of that (2,10,2,10) is just a scaled version; the simplest integer set with H⁺ = 8 is 1,5,1,5 as shown.
Correct Answer: 1, 5, 1, 5
Why the other options are incorrect:
2,10,2,10 is scaled but not simplest; 5,1,5,1 reverses ratios; 1,8,1,8 confuses H⁺ coefficient.
9. The Lewis structure of PF₃ shows how many lone pairs on phosphorus?
- 0
- 1
- 2
- 3
Explanation
Explanation:
Phosphorus trifluoride (PF₃) has phosphorus as the central atom with five valence electrons. Each of the three fluorine atoms contributes one electron to form three P–F single bonds. After forming these bonds, two electrons remain on the phosphorus atom, creating one lone pair. The resulting Lewis structure shows phosphorus surrounded by three bonding pairs and one lone pair, giving PF₃ a trigonal pyramidal shape.
Correct Answer: 1
Why the other options are incorrect:
0 lone pairs would be for PF₅; 2 or 3 would mismatch valence electrons.
Phosphorus trifluoride (PF₃) has phosphorus as the central atom with five valence electrons. Each of the three fluorine atoms contributes one electron to form three P–F single bonds. After forming these bonds, two electrons remain on the phosphorus atom, creating one lone pair. The resulting Lewis structure shows phosphorus surrounded by three bonding pairs and one lone pair, giving PF₃ a trigonal pyramidal shape.
Correct Answer: 1
Why the other options are incorrect:
0 lone pairs would be for PF₅; 2 or 3 would mismatch valence electrons.
10. Which electron configuration correctly represents an atom of nickel?
- 1s²2s²2p⁶3s²3p⁶4s²3d⁸
- 1s²2s²2p⁶3s²3p⁶3d¹⁰
- 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰
- 1s²2s²2p⁶3s²3p⁶3d⁸
Explanation
Explanation:
Nickel has an atomic number of 28, so it contains 28 electrons. Following the order of orbital filling, its correct electron configuration is 1s²2s²2p⁶3s²3p⁶4s²3d⁸. The 4s orbital fills before the 3d orbital, even though 3d has a higher energy level.
Why the other options are incorrect:
Some of the other options either omit the 4s electrons or have incorrect total electron counts.
Nickel has an atomic number of 28, so it contains 28 electrons. Following the order of orbital filling, its correct electron configuration is 1s²2s²2p⁶3s²3p⁶4s²3d⁸. The 4s orbital fills before the 3d orbital, even though 3d has a higher energy level.
Why the other options are incorrect:
Some of the other options either omit the 4s electrons or have incorrect total electron counts.
How to Order
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