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A: Oldest layer of sapwood lies just out...

A: Oldest layer of sapwood lies just outside vascualr cambium.
R: Sapwood contains actively conducting vessels and occupies central part of stem.

A

If both Assertion & Reason are true and the reason is the correct expalanation of the assertion. Then mark (1).

B

If Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)

C

If Assertion is true statement but Reason is false, then mark (3).

D

If both Assertion and Reason are false statements, then mark (4)

Text Solution

Verified by Experts

The correct Answer is:
D
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Go through the following statements (i) The cambium is generally more acitve on the inner side than on the outer. (ii) The autunn wood is darker and has a higher density than spring wood. (iii) In stem, the secondary xylem shows distinction into protoxylem and metxylem and occurs in the from of patches. (iv) The tracheids and vessels of the sapwood get plugged by the ingrowth of the adjacent parenchyma cells into thier cavities called tyloses. Which of theses are correct ?

Study carefully the following statements and select the incorrect one(s). (i). Lateralroots develop from pericycle. (ii) . Endodermis is the innermost layer of cortex (iii). Sapwood is the central, dark coloured, non-conducting part of secondary xylem.

[A]: Ringing/Girdling experiments involved removal of all tissues outside endodermis from a woody stem. [R]: The upper & lower part of the plant is at- tached by central xylem & phloem.

A cylindrical vessel of radius R=1m and height H=3m is filled with an ideal liquid up to a height of h=2 m. the contaienr with liquid is rotated about its central vertical axis such that the liquid just rises to the brim. Calculate the angular speed (omega) of the container.

Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) S_(N)^(1) mechanism is favoured in which of the following solvents:

Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) Nucleophilic substitution will be fastest in case of:

Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) S_(N)^(1) reaction will be fastest in which of the following solvents?

Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) Polar solvents make the reaction faster as they:

Read the passage given below and answer the following questions: Nucleophilic substitution reaction of haloalkane can be conducted according to both S_(N)^(1) and S_(N)^(2) mechanisms. However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group, nucleophilic reagent and solvent. Influences of halogen : No matter which mechanism the nucleophilic substitution reaction is based on, the leaving group always leave the central carbon atom with electron pair. This is just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group is , the more stable the anion formed is and it will be more easier for the leaving group to leave the central carbon atom, that is to say, the reactant is more easier to be substituted. The alkalinity order of halogen ion is I^(-) lt Br^(-) lt Cl^(-) lt F^(-) and the order of their leaving tendency should be I^(-) gt Br^(-) gt Cl^(-) gt F^(-) . Therefore, in four halides with the same alkyl and different halogens, the order of substitution reaction rate is RI gt RBr gt RCl gt RF . In addition, if the leaving group is very easy to leave, many carbocation intermediates are generated in the reaction and the reaction is based on S_(N)^(1) mechanism. If the leaving group is not easy to leave, the reaction is based on S_(N)^(2) mechanism. Influences of solvent polarity: In S_(N)^(1) reaction, the polarity of the system increases from the reactant to the transition state, because polar solvent has a greater stabilizing effect on the transition state than the reactant, thereby reduce activation energy and accelerate the reaction. In S_(N)^(2) reaction, the polarity of the system generally does not change from the reactant to the transition state and only charge dispersion occurs. At this time, polar solvent has a great stabilizing effect on Nu than the transition state, thereby increasing activation energy and slow down the reaction rate. For example, the decomposition rate (S_(N)^(1)) of tertiary chlorobutane in 25^(@)C water (dielectric constant 79) is 300000 times faster than in ethanol (dielectric constant 24). The reaction rate (S_(N)^(2)) of 2-bromopropane and NaOH in ethanol containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent polarity has influence on both S_(N)^(1) and S_(N)^(2) reactions, but with different results. Generally speaking, weak polar solvent is favorable for S_(N)^(2) reaction, while strong polar solvent is favorable for S_N^(1) reaction, because only under the action of polar solvent can halogenated hydrocarbon dissociate into carbocation and halogen ion and solvents with a strong polarity is favorable for solvation of carbocation, increasing its stability. Generally speaking, the substitution reaction of tertiary haloalkane is based on S_(N)^(1) mechanism in solvents with a strong polarity (for example, ethanol containing water). (Ding, Y. (2013). A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol. 312, pp. 433-437). Trans Tech Publications Ltd.) S_(N)^(1) reaction will be fastest in case of: