An atom of lead (Pb) has a mass number of 207. How many neutrons are in the nucleus?
A. 130
B. 125
C. 82
D. 84
We find the number of neutrons as follows
Number of neutrons
= mass number – atomic number
= 207 – 82
= 125 neutrons
Therefore, the Correct Answer is B.
More Questions on TEAS 7 Science
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Q #1: Which of the following is the atomic number of an atom that has 12 protons and 12 neutrons?
A. 144
B. 12
C. 24
D. 1
Answer Explanation
elements are arranged on the periodic table based on their atomic number. This identity is critical in evaluating the chemical families of elements in chemistry. Atoms are made of protons, neutrons, and electrons. Protons and neutrons are found in the nucleus while electrons are found outside the nucleus of the atom. It is the number of protons of an atom that gives its atomic number. Therefore, an atom with 12 protons has an atomic number of 12.
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Q #2: The ________ circulation picks up oxygen for cellular use and drops off carbon dioxide for removal from the body.
A. pulmonary
B. interlobular
C. respiratory
D. bronchial
Answer Explanation
Our blood flow is separated into two major pathways, listed below:
- Systemic circulation - this comes from the left side of the heart and pumps blood to all working tissues, including the brain, muscle, heart, and other organs, and then into the right side of the heart.
- Pulmonary system - this comes from the right side of the heart, and pumps blood to the alveolar sacs within the lungs, and then into the left side of the heart
In pulmonary circulation: The pulmonary artery is a big artery that comes from the heart. It splits into two main branches, and brings blood from the heart to the lungs. At the lungs, the blood picks up oxygen and drops off carbon dioxide.
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Q #3: A myocardial infarction affects which of the following blood vessels of the heart?
A. Aorta
B. Vena cava
C. Pulmonary
D. Coronary
Answer Explanation
A myocardial infarction refers to heart attack, which result from blockage of blood flowing into the heart.
Blocking is caused by the deposition of fat or cholesterol that forms plaque on the surface of coronary arteries, which supply blood to the heart.
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Q #4: Which of these infectious agents do not have nucleic acid?
A. viroids
B. viruses
C. bacteria
D. prions
Answer Explanation
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Q #5: Building blocks of proteins Which of the following organic molecules contain both an amine and carboxyl group?
A. Lipids
B. Proteins
C. Cellulose
D. Chitin
Answer Explanation
The basic building block of the protein is ammonia, which comprises of ammino group -NH2 and a carboxyl group, -COOH.
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Q #6: Metabolism of proteins Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?
A. Sebum
B. Urea
C. Lysozymes
D. Water
Answer Explanation
Proteins are nitrogen-based compounds, which when broken down release ammonia. Ammonia is a toxic substance to the body, and sebaceous glands coverts it to urea.
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Q #7: Which of the following best describes the result of using a catalyst in a chemical reaction?
A. A more desirable product is often formed
B. The reaction is completed in a shorter amount of time
C. The yield of product is increased
D. A greater amount of energy is released by the reaction
Answer Explanation
A catalyst is substance that speeds up the rate of converting reactants to products. They do by decreasing the activation energy of a reaction. If a catalyst increases the rate of reaction, then it means that the reaction takes a smaller time to come into completion.
Catalysts can be metals, ions or biological also known as enzymes. Catalysts are not consumed when the reaction is taking place. -
Q #8: Punnett square In a certain plant, red flowers are dominant over white flowers. A plant heterozygous for red flowers and a plant with white flowers are crossed. Which of the following is the expected proportion of phenotypes in the next generation?
A. 4 red, 0 white
B. 2 red, 2 white
C. 1 red, 3 white
D. 3 red, 1 white
Answer Explanation
We use the Punnet square to find the population of the resulting offspring from the crossing of a plant heterozygous for red flowers with a plant with white flowers.
Let R be the dominant allele for red while r is the recessive allele color for red. Therefore, the phenotype for parent 1 which is heterozygous for red flower will be Rr and the second parent with white flowers will be rr.
We cross the two phenotypes in a Punnet square as follows
r
r
R
Rr
Rr
r
rr
rr
Thus, there are 2 heterozygous offspring with red flowers and 2 offspring with white flowers.
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Q #9: Which of the following best describes veins?
A. thick walled, small lumens, low pressure, lack valves
B. thin walled, large lumens, low pressure, have valves
C. thin walled, small lumens, high pressure, have valves
D. thick walled, large lumens, high pressure, lack valves
Answer Explanation
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Q #10: The process that moves nutrients into the blood or lymph is
A. digestion
B. ingestion
C. elimination
D. absorption
Answer Explanation
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma.
Ingestion is the process of taking food, drink, or another substance into the body by swallowing or absorbing it.
Elimination refers to the removal of indigestible wastes through the anus, in the form of feaces.
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