how many ml to the appropriate number of significant figures of a 0 m stock solution of hcl should be added to water to create 250 ml of a 50 m soluti

ATI TEAS 7

ATI TEAS Science Practice Test

1. How many mL of a 0 M stock solution of HCl should be added to water to create 250 mL of a 50 M solution of HCl?

A. 31.25 mL
B. 32 mL
C. 30 mL
D. 31.3 mL

Correct answer: B

Rationale: To prepare 250 mL of a 50 M solution of HCl, the formula V1 x C1 = V2 x C2 is used, where V1 is the volume of the stock solution, C1 is the concentration of the stock solution, V2 is the final volume of the desired solution, and C2 is the final concentration of the desired solution. Given V1 x 0 M = 250 mL x 50 M, solving for V1 results in V1 = (250 mL x 50 M) / 0 M = 32 mL. Therefore, 32 mL of the 0 M stock solution of HCl needs to be added to water to create a 250 mL solution of 50 M HCl. Choices A, C, and D are incorrect because they do not represent the accurate volume required for the dilution calculation based on the given concentrations and volumes in the problem.

2. An atom has 2 protons, 4 neutrons, and 2 electrons. What is the approximate atomic mass of this atom?

A. 2
B. 4
C. 6
D. 8

Correct answer: D

Rationale: The atomic mass of an atom is the sum of the protons and neutrons in its nucleus. In this case, the atom has 2 protons and 4 neutrons, totaling 6 particles in the nucleus. Therefore, the approximate atomic mass of this atom is 6, making choice C incorrect. The number of electrons does not significantly contribute to the atomic mass, as they are much lighter and located in the electron cloud surrounding the nucleus. Choices A, B, and C are incorrect as they do not reflect the correct calculation of atomic mass based on protons and neutrons only.

3. Which hormone, produced by the pituitary gland, stimulates the growth and development of bones, muscles, and organs?

A. Growth hormone (GH)
B. Thyroid-stimulating hormone (TSH)
C. Prolactin
D. Follicle-stimulating hormone (FSH)

Correct answer: A

Rationale: The correct answer is Growth hormone (GH). GH, produced by the pituitary gland, is responsible for stimulating the growth and development of bones, muscles, and organs. It plays a critical role in regulating growth during childhood and adolescence by promoting cell division, protein synthesis, and tissue growth. Thyroid-stimulating hormone (TSH) functions to stimulate the thyroid gland to produce thyroid hormones, while prolactin is involved in milk production. Follicle-stimulating hormone (FSH) is primarily responsible for reproductive functions like egg development in females and sperm production in males.

4. What information can be obtained from the mass number of an element?

A. The number of protons in the nucleus
B. The total number of protons and neutrons
C. The number of electrons in the valence shell
D. The element's chemical reactivity

Correct answer: B

Rationale: The mass number of an element represents the total number of protons and neutrons in the nucleus. This information is crucial for determining the atomic mass of the element and understanding its stability and isotopes. The number of protons in the nucleus (option A) is represented by the atomic number, not the mass number. The number of electrons in the valence shell (option C) is related to the element's position in the periodic table and its chemical properties, but it is not directly determined by the mass number. The element's chemical reactivity (option D) is influenced by the number and arrangement of electrons in the atom's energy levels, not by the mass number.

5. Which of the following organs is part of the central nervous system?

A. Heart
B. Brain
C. Liver
D. Lungs

Correct answer: B

Rationale: The correct answer is B: Brain. The brain is a vital organ that is part of the central nervous system, along with the spinal cord. It plays a crucial role in processing information, controlling body functions, and coordinating responses to stimuli. The heart, liver, and lungs are not part of the central nervous system; they belong to the cardiovascular and respiratory systems, respectively. The heart is part of the cardiovascular system, responsible for pumping blood throughout the body. The liver is part of the digestive system, involved in processes like detoxification and metabolism. The lungs are part of the respiratory system, facilitating the exchange of oxygen and carbon dioxide during breathing.