In the following single-replacement reaction, ______ replaces ______. Cl2+2NaI→2NaCl+I2
A. sodium, iodine
B. chlorine, iodine
C. chlorine, sodium
D. sodium, chlorine
In this reaction, chlorine (Cl2) is an element in the reaction that replaces iodine in the compound sodium iodide (NaI). This allows chlorine to form a compound with sodium (NaCl) and leaves iodine (I2) as an element.
Synthesis reactions involve two or more reactants (A and B) combining to form one product (AB). In the example provided, hydrogen (H2) and oxygen (O2) begin as separate elements. At the end of the reaction, the hydrogen and oxygen atoms are bonded in a molecule of water (H2O).
Decomposition reactions have only one reactant (AB) that breaks apart into two or more products (A and B). In the example above, hydrogen peroxide (H2O2) breaks apart into two smaller molecules: water (H2O) and oxygen (O2).
Single-replacement reactions involve two reactants, one compound (AB) and one element (C). In this type of reaction, one element replaces another to form a new compound (AC), leaving one element by itself (B). In the example, zinc replaces hydrogen in hydrochloric acid (HCl). As a result, zinc forms a compound with chlorine, zinc chloride (ZnCl2), and hydrogen (H2) is left by itself.
Double-replacement reactions involve two reactants, both of which are compounds made of two components (AB and CD). In the example, silver nitrate, composed of silver (Ag1+) and nitrate (NO31-) ions, reacts with sodium chloride, composed of sodium (Na1+) and chloride (Cl1-) ions. The nitrate and chloride ions switch places to produce two compounds that are different from those in the reactants.
Combustion reactions occur when fuels burn, and they involve specific reactants and products, as seen in the examples below. Some form of fuel that contains carbon and hydrogen is required. Examples of such fuels are methane, propane in a gas grill, butane in a lighter, and octane in gasoline. Notice that these fuels all react with oxygen, which is necessary for anything to burn. In all combustion reactions, carbon dioxide, water, and energy are produced. When something burns, energy is released, which can be felt as heat and seen as light.
Therefore, the Correct Answer is B.
More Questions on TEAS 7 Science
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Q #1: Where is skeletal muscle found?
A. Inside the heart
B. Attached to bone
C. Lining the walls of the bladder
D. Within the gastrointestinal tract
Answer Explanation
Skeletal muscle: This muscle cell is striated, long, and cylindrical. There are many nuclei in a skeletal muscle cell. Attached to bones in the body, skeletal muscle contracts voluntarily, meaning that it is under conscious control.
Smooth muscle: This muscle consists of nonstriated muscle cells that are spindle-shaped. Like cardiac muscle cells, smooth muscle cells contain one nucleus. This muscle type is found in the walls of internal organs like the bladder and stomach. Smooth muscle contraction is involuntary and controlled by the autonomic nervous system.
Cardiac muscle: This muscle consists of muscle cells that are striated, short, and branched. These cells contain one nucleus, are branched, and are rectangular. Cardiac muscle contraction is an involuntary process, which is why it is under the control of the autonomic nervous system. This muscle is found in the walls of the heart.
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Q #2: During the aging process, not all hormone levels decrease; some actually increase. Which of the following is a hormone that may increase as a person ages?
A. Cortisol
B. Insulin
C. Luteinizing
D. Thyroid
Answer Explanation
The aging process affects hormone activity in one of three ways: their secretion can decrease, remain unchanged, or increase.
Hormones that decrease secretion include the following:
- Estrogen (in women)
- Testosterone (in men)
- Growth hormone
- Melatonin
In women, the decline in estrogen levels leads to menopause. In men, testosterone levels usually decrease gradually. Decreased levels of growth hormone may lead to decreased muscle mass and strength. Decreased melatonin levels may play an important role in the loss of normal sleep-wake cycles (circadian rhythms) with aging.
Hormones that usually remain unchanged or slightly decrease include the following:
- Cortisol
- Insulin
- Thyroid hormones
Hormones that may increase secretions levels include the following:
Parathyroid hormone
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Norepinephrine
- Epinephrine, in the very old
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Q #3: Which of the following are included in the male reproductive system?
A. the penis and epididymis
B. the vas deferens and uterus
C. the penis and Fallopian tubes
D. the penis, scrotum, and cervix
Answer Explanation
The main male reproductive organs are the penis and the testicles, which are located external to the body. The penis is composed of a long shaft and a bulbous end called the glans penis. The glans penis is usually surrounded by an extension of skin called the foreskin.
The testes (analogous to the female ovaries), or testicles, are retained in a pouch of skin called the scrotum, which descends from the base of the penis. The scrotum contains nerves and blood vessels needed to support the testicles’ functions. Each testicle (or testis) produces sperm (analogous to the female ova), which are passed into a series of coiled tubules called the epididymis. The epididymis stores and nurtures sperm until they are passed into the vas deferens, a tubule that is about 30 centimeters long, extending from the testicle into the pelvis and ending at the ejaculatory duct.
The epididymis and vas deferens are supported by several accessory glands (the seminal vesicles, the prostate gland, and the Cowper glands) that produce fluid components of semen and support the sperm cells.
