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What is the charge of noble gases?
- A. -1
- C. 1
- D. 2
Correct Answer: B
Rationale: The correct answer is B: 0. Noble gases have a charge of 0 because they have full valence shells and are inert. This makes them stable and unreactive, resulting in a charge of 0 as they do not readily gain or lose electrons. Choices A, C, and D are incorrect because noble gases do not typically form ions by gaining or losing electrons, so they do not carry a charge of -1, 1, or 2.
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What charge do Group IA elements have?
- A. +1
- B. +2
- C. +3
Correct Answer: A
Rationale: 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 are neutral particles called?
- A. Neutrons
- B. Protons
- C. Electrons
- D. Cations
Correct Answer: A
Rationale: Neutral particles, which have no electric charge, are known as neutrons. Neutrons are found in the nucleus of an atom along with protons. Electrons carry a negative charge and orbit the nucleus. Cations are positively charged ions formed by losing electrons. Therefore, the correct answer is 'Neutrons' as they are the neutral particles in an atom, unlike protons, electrons, or cations.
How does increasing the concentration of reactants affect a chemical reaction?
- A. Decreases the reaction rate
- B. Increases the reaction rate
- C. Stops the reaction
- D. Has no effect
Correct Answer: B
Rationale: Increasing the concentration of reactants leads to more reactant particles being available, which, in turn, increases the likelihood of successful collisions between particles. This higher frequency of collisions results in a higher reaction rate. Therefore, option B, 'Increases the reaction rate,' is the correct answer. Choice A, 'Decreases the reaction rate,' is incorrect because higher reactant concentration usually speeds up the reaction. Choice C, 'Stops the reaction,' is incorrect as increasing concentration promotes more collisions, enhancing the reaction. Choice D, 'Has no effect,' is incorrect because changing reactant concentration directly impacts the reaction rate in most cases.
What type of chemical reaction involves the reaction of a compound with oxygen?
- A. Decomposition
- B. Synthesis
- C. Combustion
- D. Single replacement
Correct Answer: C
Rationale: The correct answer is C: Combustion. A combustion reaction is characterized by a compound reacting with oxygen. During this process, heat and light are often produced as energy is released in the form of heat. Combustion is a common type of reaction involving organic compounds, like hydrocarbons, reacting with oxygen to produce carbon dioxide and water. Choices A, B, and D are incorrect because decomposition involves a compound breaking down into simpler substances, synthesis involves the combination of two or more substances to form a more complex one, and single replacement involves an element replacing another element in a compound.
What can stop the penetration of alpha particles?
- A. Aluminum foil
- B. Glass
- C. Piece of paper
- D. Plastic
Correct Answer: C
Rationale: Alpha particles can be stopped by a piece of paper due to their low penetration power. The paper acts as a shield, effectively blocking the alpha particles from passing through. In contrast, materials like aluminum foil, glass, and plastic are not as effective as a simple piece of paper in stopping alpha particles. Aluminum foil is more effective against beta particles, gamma rays, and x-rays due to its higher density. Glass and plastic also provide some protection against beta particles and gamma rays, but they are less effective than a piece of paper against alpha particles.