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. Which of the following is the primary physical barrier the body uses to prevent infection?

A. mucus membranes
B. stomach acid
C. skin
D. urine

Correct answer: C

Rationale: The correct answer is 'C: skin.' The skin is the primary physical barrier the body uses to prevent infection. It acts as a protective shield that prevents harmful microorganisms from entering the body. The outer layer of the skin, known as the epidermis, acts as a tough physical barrier that blocks the entry of pathogens. Additionally, the skin has special immune cells that can help fight off invaders that manage to breach the physical barrier. Choices A, B, and D are incorrect. While mucous membranes, stomach acid, and urine play important roles in the body's defense against pathogens, the primary physical barrier is the skin, which covers the entire body and provides a robust protective barrier.

3. If a doctor diagnoses a patient with an impaired posterior pituitary gland, which of the following symptoms related to kidney function does the patient display?

A. Thirst
B. Tiredness
C. Weight gain
D. Concentrated urine

Correct answer: D

Rationale: When the posterior pituitary gland is impaired, there is decreased secretion of antidiuretic hormone (ADH). ADH plays a crucial role in regulating water reabsorption by the kidneys. A deficiency of ADH leads to the inability of the kidneys to concentrate urine, resulting in the production of dilute urine. Therefore, 'Concentrated urine' is the correct symptom associated with impaired posterior pituitary gland. Choices A, B, and C are incorrect. Thirst is more commonly associated with diabetes insipidus, tiredness could be a general symptom but not specifically related to kidney function, and weight gain is not a typical symptom of impaired posterior pituitary gland affecting kidney function.

4. What is the role of the hypothalamus in the body?

A. To regulate digestion
B. To regulate hormones
C. To regulate body temperature
D. To regulate the immune system

Correct answer: B

Rationale: The correct answer is B: 'To regulate hormones.' The hypothalamus plays a crucial role in regulating hormones and maintaining homeostasis by controlling various functions such as hunger, thirst, body temperature, and sleep-wake cycles. While digestion, body temperature, and the immune system are important bodily functions, they are not primarily controlled by the hypothalamus. Therefore, choices A, C, and D are incorrect as they do not accurately represent the primary function of the hypothalamus.

5. What is the main function of the nervous system?

A. To fight infection
B. To control body movement and coordination
C. To regulate metabolism
D. To transport oxygen

Correct answer: B

Rationale: The main function of the nervous system is to control body movement and coordination by transmitting signals between different parts of the body. Choice A is incorrect because the immune system, not the nervous system, is primarily responsible for fighting infections. Choice C is incorrect as regulating metabolism is primarily handled by the endocrine system. Choice D is incorrect because the transportation of oxygen is mainly the function of the circulatory system, specifically the blood.