Weekly topic: 5 Wealth points for those who answer correctly, 2 Wealth points for participation； Question 144
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Multiple choice: Phenolic resin can be prepared by reacting phenol with formaldehyde. When preparing phenolic resin in the laboratory, under acidic conditions, if the phenolic resin obtained with an excess of phenol is difficult to separate, some ethanol can be added while the mixture is still hot to help remove the resin ； Under alkaline conditions, when phenol is in excess, if the phenolic resin is difficult to remove, it is hard to extract the resin using either heating or the addition of solvents. In the above two cases, which of the following statements is correct? ( ) A. Linear phenolic resin is obtained under acidic conditions, while network-shaped phenolic resin is obtained under alkaline conditions. B. Three-dimensional phenolic resin is obtained under acidic conditions, while linear phenolic resin is obtained under alkaline conditions. C. Linear phenolic resin is obtained in both conditions. D. Network-shaped phenolic resin is obtained in both conditions. Answer: A. Explanation: Organic polymers with a linear structure can dissolve in appropriate solvents; under acidic conditions, the resulting phenolic resin can dissolve in alcohol, indicating that it is linear in structure ； Organic polymers with a specific structural framework are not easily soluble ； There is only a certain degree of swelling; therefore, under alkaline conditions, a network-like structure is obtained.
Analysis: Organic polymers with a linear structure can dissolve in appropriate solvents. Under acidic conditions, the resulting phenol-formaldehyde resin can dissolve in alcohol, which indicates that it has a linear structure； Organic polymers with a network-like structure are not easily soluble; they only swell to a certain extent. Therefore, under alkaline conditions, a network-shaped structure is obtained. Answer: A
Phenol-formaldehyde resin can be produced by reacting phenol with formaldehyde. When preparing phenolic resin in the laboratory, under acidic conditions, if the phenolic resin obtained with an excess of phenol is difficult to separate, some ethanol can be added while the mixture is still hot to help remove the resin ； Under alkaline conditions, when phenol is in excess, if the phenolic resin is difficult to remove, it is hard to extract the resin using either heating or the addition of solvents. In the above two cases, the correct statement among the following is (B)
A. Linear phenolic resins are obtained under acidic conditions, while network-shaped phenolic resins are formed under alkaline conditions
A. Linear phenolic resins are obtained under acidic conditions, while network-shaped phenolic resins are formed under alkaline conditions
A. Linear phenolic resins are obtained under acidic conditions, while network-shaped phenolic resins are formed under alkaline conditions
Phenol-formaldehyde resin can be produced by reacting phenol with formaldehyde. When preparing phenolic resin in the laboratory, under acidic conditions, if the phenolic resin obtained with an excess of phenol is difficult to separate, some ethanol can be added while the mixture is still hot to help remove the resin ； Under alkaline conditions, when phenol is in excess, if the phenolic resin is difficult to remove, it is hard to extract the resin using either heating or the addition of solvents. In both of the above cases, the correct statement among the following is (A). Answer: A. Hint: Organic polymers with a linear structure can dissolve in appropriate solvents; under acidic conditions, the resulting phenol-formaldehyde resin can dissolve in alcohol, which indicates that it has a linear structure ； Organic polymers with a specific structural framework are not easily soluble ； There is only a certain degree of swelling; therefore, under alkaline conditions, a network-like structure is obtained
Multiple choice: Phenolic resin can be prepared by reacting phenol with formaldehyde. When preparing phenolic resin in the laboratory, under acidic conditions, if the phenolic resin obtained with an excess of phenol is difficult to separate, some ethanol can be added while the mixture is still hot to help remove the resin ； Under alkaline conditions, when phenol is in excess, if the phenolic resin is difficult to remove, it is hard to extract the resin using either heating or the addition of solvents. In the above two cases, which of the following statements is correct? (A) A. Linear phenolic resins are obtained under acidic conditions, while network-shaped phenolic resins are obtained under alkaline conditions. B. Three-dimensional phenolic resins are obtained under acidic conditions, while linear phenolic resins are obtained under alkaline conditions. C. Linear phenolic resins are obtained in both conditions. D. Network-shaped phenolic resins are obtained in both conditions
Phenol-formaldehyde resin can be produced by reacting phenol with formaldehyde. When preparing phenolic resin in the laboratory, under acidic conditions, if the phenolic resin obtained with an excess of phenol is difficult to separate, some ethanol can be added while the mixture is still hot to help remove the resin ； Under alkaline conditions, when phenol is in excess, if the phenolic resin is difficult to remove, it is hard to extract the resin using either heating or the addition of solvents. In the above two cases, the correct statement is (B). A. Linear phenolic resins are obtained under acidic conditions, while network-shaped phenolic resins are obtained under alkaline conditions. B. Three-dimensional phenolic resins are obtained under acidic conditions, while linear phenolic resins are obtained under alkaline conditions. C. Linear phenolic resins are obtained in both conditions. D. Network-shaped phenolic resins are obtained in both conditions
Multiple choice: Phenolic resin can be prepared by reacting phenol with formaldehyde. When preparing phenolic resin in the laboratory, under acidic conditions, if the phenolic resin obtained with an excess of phenol is difficult to separate, some ethanol can be added while the mixture is still hot to help remove the resin ； Under alkaline conditions, when phenol is in excess, if the phenolic resin is difficult to remove, it is hard to extract the resin using either heating or the addition of solvents. In the above two cases, which of the following statements is correct? ( ) A. Linear phenolic resin is obtained under acidic conditions, while a network-type phenolic resin is obtained under alkaline conditions