HESI A2
Chemistry Hesi A2
1. Balance this equation: Zn + HCl → ZnCl + H2.
- A. Zn + 2HCl → ZnCl + H2
- B. Zn + HCl → 2ZnCl + H2
- C. 2Zn + 2HCl → 2ZnCl + H2
- D. Zn + 4HCl → ZnCl + H2
Correct answer: C
Rationale: The given unbalanced equation is Zn + HCl → ZnCl + H2. To balance it, we need to have equal atoms on both sides of the equation. The balanced equation is 2Zn + 2HCl → 2ZnCl + H2. This balanced equation shows that two atoms of Zn combine with two molecules of HCl to form two molecules of ZnCl and one molecule of H2. Choice A is incorrect because it does not balance the equation. Choice B is incorrect as it does not have the same number of atoms on both sides. Choice D is incorrect because it does not balance the equation properly, resulting in an unequal number of atoms on both sides.
2. What are the 3 types of radiation in nuclear chemistry?
- A. Alpha, Beta, Delta
- B. Alpha, Beta, Gamma
- C. Gamma, Beta, Delta
- D. Delta, Beta, Gamma
Correct answer: B
Rationale: The correct answer is B: Alpha, Beta, Gamma. In nuclear chemistry, the 3 types of radiation are alpha, beta, and gamma radiation. Alpha radiation consists of helium nuclei, beta radiation involves electrons or positrons, and gamma radiation is electromagnetic radiation of high frequency. Choice A is incorrect because 'Delta' is not a type of radiation in nuclear chemistry. Choice C is incorrect as it does not list alpha radiation. Choice D is incorrect as it lists the types in the wrong order and includes 'Delta' instead of alpha radiation.
3. What form of radiation is composed of electrons traveling at around 16,000 km/sec?
- A. Alpha radiation
- B. Beta radiation
- C. Gamma radiation
- D. Delta radiation
Correct answer: B
Rationale: Beta radiation is composed of high-energy electrons (β- particles) or positrons (β+ particles) traveling at considerable speeds. In this case, the electrons traveling at around 16,000 km/sec align with the characteristics of beta radiation, making it the correct choice. Alpha radiation consists of helium nuclei, gamma radiation is electromagnetic radiation of high frequency, and delta radiation is not a recognized form of radiation, making them all incorrect choices.
4. Which element has the chemical symbol 'Fe'?
- A. Lead
- B. Iron
- C. Silver
- D. Copper
Correct answer: B
Rationale: The correct answer is 'Iron' as it has the chemical symbol 'Fe'. Chemical symbols are used to represent elements in the periodic table, and 'Fe' specifically refers to Iron. Choice A, Lead, is incorrect as the chemical symbol for Lead is 'Pb'. Choice C, Silver, is incorrect as the chemical symbol for Silver is 'Ag'. Choice D, Copper, is incorrect as the chemical symbol for Copper is 'Cu'. Therefore, 'Iron' is the only element among the choices with the chemical symbol 'Fe'.
5. What type of chemical reaction involves the combination of two elements to form a product?
- A. Decomposition
- B. Combustion
- C. Synthesis
- D. Double replacement
Correct answer: C
Rationale: A synthesis reaction involves the combination of two or more substances to form a single, more complex product. In the context of chemical reactions, it specifically refers to the combination of two elements to form a compound. Therefore, the correct answer is C. Decomposition reactions involve the breakdown of a single compound into simpler substances (opposite of synthesis). Combustion reactions involve a substance reacting with oxygen to produce heat and light, not the combination of elements. Double replacement reactions involve the exchange of ions between two compounds, leading to the formation of two new compounds, not the combination of two elements.
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