CHEM 120 W8 Exam3 and W8 Lab Practicum at Chamberlain University
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Free CHEM 120 W8 Exam3 and W8 Lab Practicum at Chamberlain University Questions
Which of the following are ways healthcare workers protect themselves from ionizing radiation? Select all that apply.
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Decrease time of exposure
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Wear a lead apron
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Drink plenty of water before
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Increase distance from source
Explanation
A. Decrease time of exposure
Limiting the amount of time spent near a radiation source minimizes the total dose absorbed. The less time a worker spends exposed, the smaller the risk of cellular damage or long-term health effects.
B. Wear a lead apron
Lead aprons provide an effective barrier against ionizing radiation, especially during diagnostic imaging procedures like X-rays. The dense lead material absorbs radiation, protecting vital organs and reducing exposure to reproductive and bone marrow tissues.
D. Increase distance from source
Radiation intensity decreases sharply with distance, following the inverse square law. By maximizing distance from the radiation source, healthcare workers significantly reduce their exposure and risk, even without heavy shielding.
Which is the best description of rRNA?
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It is part of the ribosome
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It holds the entire genetic code
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It carries a copy of the DNA code to the ribosome
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It carries the amino acid to the ribosome
Explanation
Ribosomal RNA (rRNA) forms the structural and functional core of ribosomes, the cellular organelles responsible for protein synthesis. It helps align messenger RNA (mRNA) and transfer RNA (tRNA) during translation and catalyzes the formation of peptide bonds between amino acids. rRNA thus plays a direct enzymatic and structural role in building proteins, making it essential for gene expression and cellular function.
In order to protect yourself from radiation, it is important to know which type of radiation penetrates most deeply into the body. Which type of ionizing radiation would you expect to penetrate most deeply into your body?
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Gamma rays
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Visible light
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Beta decay particles
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Alpha decay particles
Explanation
Gamma rays are high-energy electromagnetic waves with no mass or charge, allowing them to penetrate deeply through most materials, including human tissue. Unlike alpha and beta particles, which are stopped by skin or thin barriers, gamma rays require dense shielding like lead or concrete. This deep penetration makes gamma radiation the most hazardous type of ionizing radiation for internal exposure and one of the most challenging to shield against effectively.
Which form of radiation is able to penetrate most deeply into the human body?
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Alpha decay
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Gamma ray emission
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Skin would block all of these types of radiation
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Beta decay
Explanation
Gamma rays are high-energy electromagnetic waves with no mass and no charge, allowing them to penetrate deeply through human tissue and even several centimeters of lead or concrete. Because of their penetrating power, they pose a significant internal and external radiation hazard.
Why does the correct Lewis structure of CO2 involve a double bond between each of the oxygen atoms and the carbon atom?
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To complete the octet for carbon
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Because the oxygens would otherwise have more than eight electrons
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Because carbon is more electronegative than oxygen
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To emphasize that it's a covalent bond
Explanation
In the Lewis structure of CO₂, carbon needs four additional electrons to complete its octet, while each oxygen needs two. By forming two double bonds—one between carbon and each oxygen—both the carbon and oxygen atoms achieve stable octets. This arrangement minimizes formal charges and accurately represents the molecule’s bonding, showing that CO₂ is a linear molecule with strong covalent bonds between atoms.
A medical isotope has a half-life of 20 minutes. If you have 400 grams of this freshly prepared isotope, how many grams will remain after 60 minutes?
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20 g
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50 g
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3 g
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100 g
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200 g
Explanation
The half-life is 20 minutes, meaning the quantity halves every 20 minutes.
Start: 400 g
After 20 minutes: 400 g ÷ 2 = 200 g
After 40 minutes: 200 g ÷ 2 = 100 g
After 60 minutes: 100 g ÷ 2 = 50 g
Thus, after 60 minutes (3 half-lives), 50 g remains.
The enzyme OREOase acts on chocolate sandwich cookies to break the cookies apart to get to the creamy center. Occasionally, a vanilla cookie also fits into the OREOase active site, but the enzyme cannot act on the vanilla cookie so the reaction halts. Eventually, the vanilla cookie leaves the active site. What is the best description of the vanilla cookie in this scenario?
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Competitive inhibitor
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Denaturing of the protein
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Cofactor
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Coenzyme
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Non-competitive inhibitor
Explanation
A competitive inhibitor is a substance that resembles the enzyme’s normal substrate and competes for binding at the active site. In this case, the vanilla cookie fits into OREOase’s active site just like the chocolate cookie (the true substrate) but does not undergo a reaction. This temporarily blocks the enzyme’s activity until the inhibitor leaves, allowing the correct substrate to bind again.
A long chain of glucose molecules forms. Which of the following terms would best describe the resulting biomolecule?
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Monosaccharide
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Polysaccharide
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Sugar
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Disaccharide
Explanation
A polysaccharide is a complex carbohydrate composed of many glucose (monosaccharide) units bonded together through glycosidic linkages. Examples include starch, glycogen, and cellulose. These large molecules serve important biological functions such as energy storage (starch in plants, glycogen in animals) and structural support (cellulose in plant cell walls).
If a person's body suddenly became unable to do the process of translation, what biomolecule class would you be immediately unable to produce?
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Proteins
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DNA
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Carbohydrates
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Lipids
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RNA
Explanation
Translation is the cellular process in which ribosomes read messenger RNA (mRNA) to assemble amino acids into specific protein sequences. If translation stops, the body cannot produce proteins—essential molecules responsible for structure, enzymes, transport, and signaling. Without protein synthesis, nearly all cellular functions, including metabolism, growth, and repair, would cease, leading to system-wide failure in biological processes.
What happens to the atomic number during alpha decay?
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It can increase or decrease, depending on the atom.
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There is no change in mass because electrons have essentially no mass.
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It always increases, since two protons are expelled from the nucleus.
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It always decreases, since two protons are expelled from the nucleus.
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It always increases, since two neutrons are expelled from the nucleus.
Explanation
During alpha decay, an unstable nucleus emits an alpha particle, which consists of two protons and two neutrons. Because two protons are lost, the element’s atomic number decreases by two, transforming it into a different element lower on the periodic table. For example, when uranium-238 undergoes alpha decay, it becomes thorium-234, as its atomic number drops from 92 to 90.
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