Nokea
How many hydrogen atoms are present in the reactants?
- A. 2
- B. 4
- C. 1
- D. None of the above
Correct Answer: B
Rationale: To determine the number of hydrogen atoms in the reactants, we need to examine the chemical formula of the reactants. If the formula contains hydrogen atoms, we count them to find the total. In this case, the correct answer is 4 because there are 4 hydrogen atoms present in the reactants. The chemical formula in the reactants indicates the presence of 4 hydrogen atoms. It is crucial to pay close attention to the elements and their quantities in chemical reactions to ensure accurate analysis and understanding of reactants and products.
You may also like to solve these questions
What is the charge on potassium in the compound KCl?
- A. -1
- B. +1
- C. -2
- D. +2
Correct Answer: B
Rationale: In the compound KCl, the overall charge must be zero since it is a neutral compound. Chlorine (Cl) typically has a charge of -1 in ionic compounds. Therefore, for the compound to be neutral, potassium (K) must have a charge of +1 to balance the -1 charge of chlorine. This results in a total charge of 0 for the compound. Thus, the correct answer is +1. The positively charged potassium ion (K+) combines with the negatively charged chloride ion (Cl-) to form an electrically neutral compound, potassium chloride (KCl).
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.
- A. 1.59 g/mL
- B. 2.76 g/mL
- C. 1.4 g/mL
- D. None are correct.
Correct Answer: A
Rationale: 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.
An element has 6 protons, 6 electrons, and 6 neutrons. What is its atomic number?
- A. 6
- B. 12
- C. 18
- D. Not enough information
Correct Answer: A
Rationale: The atomic number of an element is determined by the number of protons in its nucleus. Since the element in question has 6 protons, its atomic number is also 6. The number of neutrons and electrons does not impact the atomic number, which is solely based on the number of protons. Therefore, the correct answer is A: 6.
Which of the following substances is the most dense?
- A. A block of gold weighing 12g and occupying 4.6cm³
- B. A cube weighing 6g and having a volume of 0.91cm³
- C. A block weighing 143g and with a volume of 24.3cm³
- D. None of the above
Correct Answer: B
Rationale: Density is calculated by dividing the mass of an object by its volume. For Choice A, the density is 12 g / 4.6 cm³ = 2.61 g/cm³. For Choice B, the density is 6 g / 0.91 cm³ = 6.59 g/cm³, making it the most dense option. For Choice C, the density is 143 g / 24.3 cm³ = 5.88 g/cm³. Therefore, Choice B, the cube weighing 6 g and having a volume of 0.91 cm³, is the most dense substance among the options provided.
What does carbonic acid become within the human body?
- A. Digests food
- B. Kills viruses
- C. Maintains pH of blood
- D. Grows hair
Correct Answer: C
Rationale: Carbonic acid, formed when carbon dioxide dissolves in water, plays a crucial role in maintaining the pH balance of the blood. It acts as a buffer to prevent drastic changes in blood pH, which is vital for the body's proper functioning. Carbonic acid does not digest food, kill viruses, or contribute to hair growth. Therefore, options A, B, and D are incorrect roles of carbonic acid within the human body, making maintaining the pH of blood (Option C) the correct answer.