In the following single-replacement reaction, ______ replaces ______.
Cl2+2NaI→2NaCl+I2
sodium, iodine
chlorine, iodine
chlorine, sodium
sodium, chlorine
Correct Answer : B
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.
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Related Questions
Correct Answer is D
Explanation
The duodenum is the first part of the small intestines, located between the stomach and the middle part of the small intestines (jejunum). Once food has mixed with acid in the stomach, it moves into the duodenum, where it then mixes with bile from the gallbladder and digestive juices secreted from the pancreas. In the duodenum, absorption of vitamins, minerals, and nutrients begins.
Correct Answer is D
Explanation
The autonomic nervous systemis responsible for activities that arenonvoluntaryand under unconscious control. This system controls glands and the smooth muscles of internal organs, heart rate, breathing, and digestion. The autonomic nervous system is further divided into the following:
- Sympathetic nervous system: The sympathetic nervous system focuses on emergency situations by preparing the body forfight or flight. (Sympathetic = Stress)
- Parasympathetic nervous system: The parasympathetic nervous system controls involuntary processes unrelated to emergencies. This system deals with “rest or digest” activities. (Parasympathetic = Peace)
Thesomatic nervous systemprimarily controlsvoluntaryactivities such as walking and riding a bicycle. Thus, this system sends information to the CNS and motor nerve fibers that are attached to skeletal muscle.
Correct Answer is D
Explanation
In this reaction, two elements are trading places hence double-replacement. In the reactants, zinc and bromide ions are together, and potassium and hydroxide ions are together. In the products, zinc and hydroxide ions are together, and potassium and bromide ions are together.
Correct Answer is A
Explanation
The cell cycle is an organized process divided into two phases:interphaseand theM (mitotic) phase. During interphase, the cell grows and copies its DNA. After the cell reaches the M phase, division of the two new cells can occur. The G1, S, and G2phases make up interphase.
- G1:The first gap phase, during which the cell prepares to copy its DNA
- S:The synthesis phase, during which DNA is copied
- G2:The second gap phase, during which the cell prepares for cell division
It may appear that little is happening in the cell during the gap phases. Most of the activity occurs at the level of enzymes and macromolecules. The cell produces things like nucleotidesfor synthesizing new DNA strands, enzymes for copying the DNA, and tubulin proteins for building the mitotic spindle. During the S phase, the DNA in the cell doubles, but few other signs are obvious under the microscope. All the dramatic events that can be seen under a microscope occur during the M phase: the chromosomes move, and the cell splits into two new cells with identical nuclei.
Correct Answer is D
Explanation
A neutralization reaction is a type of acid-base reaction where an acid and base react to form a salt and water.
In an aqueous solution, a base increases the hydroxide concentration (OH–), while an acid increases the hydrogen ion (H+) concentration. Sometimes,neutralization reactionsalso occur. This type of reaction happens when an acid and a base react with each other to form water and salt. Salt is typically defined as anionic compoundthat includes any cation except H+and any anion except OH–. Consider the following example of a neutralization reaction between hydrobromic acid (HBr) and potassium hydroxide (KOH).
HBr+KOH→KBr+H2O
Not all neutralization reactions proceed in the manner where all reactants are in the aqueous phase. In some chemical reactions, one reactant may be a solid. The neutralization reaction can still proceed to completion.
Correct Answer is C
Explanation
One step of the scientific method is to analyze information or data collected from the experiment to conclude whether the hypothesis is supported.
Recall that these make up thescientific method,described below:
- Problem:The question created because of an observation.Example: Does the size of a plastic object affect how fast it naturally degrades in a lake?
- Research:Reliable information available about what is observed.Example: Learn how plastics are made and understand the properties of a lake.
- Hypothesis:A predicted solution to the question or problem.Example: If the plastic material is small, then it will degrade faster than a large particle.
- Experiment:A series of tests used to evaluate the hypothesis. Experiments consist of anindependent variablethat the researcher modifies and adependent variablethat changes due to the independent variable. They also include acontrol groupused as a standard to make comparisons.
- Example: Collect plastic particles both onshore and offshore of the lake over time. Determine the size of the particles and describe the lake conditions during this time period.
- Observe:Analyze data collected during an experiment to observe patterns.
- Example: Analyze the differences between the numbers of particles collected in terms of size.
- Conclusion:State whether the hypothesis is rejected or accepted and summarize all results.
- Communicate:Report findings so others can replicate and verify the results.
Correct Answer is D
Explanation
The primary function of the respiratory system is to provide oxygen to and remove carbon dioxide from the body. In addition to gas exchange, the respiratory system enables a person to breathe. Breathing, or inhalation, is essential to life. It is the mechanism that provides oxygen to the body. Without oxygen, cells are unable to perform their functions necessary to keep the body alive. The primary muscle of inspiration is the diaphragm. Known as the chest cavity, this dome shaped structure flattens when it contracts. The rib cage moves outward, allowing outside air to be drawn into the lungs. During relaxation, the diaphragm returns to its dome shape and the rib cage moves back to its natural position. This causes the chest cavity to push air out of the lungs.
The respiratory system can be functionally divided into two parts:
- Air-conducting portion: Air is delivered to the lungs. This region consists of the upper and lower respiratory tract—specifically, the larynx, trachea, bronchi, and bronchioles.
- Gas exchange portion: Gas exchange takes place between the air and the blood. This portion includes the lungs, alveoli, and capillaries.
Correct Answer is D
Explanation
In solids, particles are usually closer together than in other states of matter because of the strong cohesive forces between the particles.
- Solids, liquids, gases, and plasmas differ from one another in the amount of energy that the particles have and the strength of the cohesive forces that hold the particles together.
- Cohesion is the tendency of particles of the same kind to stick to each other.
- A solid has the lowest amount of energy because its particles are packed close together. Liquids have more energy than a solid, and gases have more energy than solids or liquids because the cohesive forces are very weak.
Correct Answer is B
Explanation
Mendel was accurately able to predict the patterns of heredity by studying rules related to genetics. These rules helped shape his theory of heredity. Heredity is the characteristics offspring inherit from their parents.
From experiments with garden peas, Mendel developed a simple set of rules that accurately predicted patterns of heredity. He discovered that plants eitherself-pollinateorcross-pollinate, when the pollen from one plant fertilizes the pistil of another plant. He also discovered that traits are eitherdominantorrecessive. Dominant traits are expressed, and recessive traits are hidden.
Mendel’s Theory of Heredity
To explain his results, Mendel proposed a theory that has become the foundation of the science of genetics. The theory has five elements:
- Parents do not transmit traits directly to their offspring. Rather, they pass on units of information calledgenes.
- For each trait, an individual has two factors: one from each parent. If the two factors have the same information, the individual ishomozygousfor that trait. If the two factors are different, the individual isheterozygousfor that trait. Each copy of a factor, orgene, is called anallele.
- The alleles determine the physical appearance, orphenotype. The set of alleles an individual has is itsgenotype.
- An individual receives one allele from each parent.
- The presence of an allele does not guarantee that the trait will be expressed.
Correct Answer is D
Explanation
Once the food has been masticated in the oral cavity (mouth), it is then swallowed and travels back into the pharynx down into the esophagus, which leads into the stomach.
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