Answer:
Only 3 is correct.
Explanation:
The crystal of a metal or an ionic compound is called a cell, and there are 7 types of unit cells: cubic, tetragonal, orthorhombic, monoclinic, hexagonal, rhombohedral, and triclinic.
In a face-centered cubic cell (FCC) all angles are 90º and all lengths are equal. Each cubic cell has 8 atoms in each corner of the cube, and that atom is shared with 8 neighboring cells. So for a metal crystal, the atom is located at each of the eight lattice points, where it is shared equally between eight unit cells.
Answer: Mixture: Blood , Self raising flour,muesli ,dyes, milk, tea, air, bronze
Pure substance: Copper wire, distilled water, table salt, oxygen.
Explanation:
Mixture is a substance which is made up two or more number of compounds which chemically inactive and retain their distinct chemical properties.
Blood , Self raising flour,muesli ,dyes, milk, tea, air, bronze
Pure substance is defined as anything with uniform and unchanging composition is known s pure substance.
Copper wire, distilled water, table salt, oxygen.
Here we have to get the correct statements among the given, applicable for Diels-Alder reaction.
The true statements in case Diels-Alder reaction are-
1. An excess of Maleic anhydride is used.
2. The I.R. of the products are indistinguishable.
The Diels-Alder reaction is the most is the most important cyclo-addition reaction in organic chemistry. These are addition reactions in which ring systems are formed without eliminating any compounds.
There remains one diene and one dienophile. The reaction is reversible in nature and requires elevated temperature to obtain its transition state. The reaction rate become faster in certain condition like using of polar solvents.
Among the given statements the following statements are true-
1. An excess of maleic anhydride (the most effective di-enophile) is used to process the reaction in forward direction.
2. The products obtain in this reaction are stereoisomers thus are indistinguishable by infrared spectroscopy (IR).
The statements which are not true for the Diels-Alder reaction:
3. The re-crystallization of the products by any polar solvent like methanol is not feasible as it will cause the retro reaction due to stability of the transition state in polar solvent.
4. Cleaning of glassware are compulsory for any reaction it is not specifically true for Diels-Alder reaction.
5. The reaction occurs at elevated temperature thus flame is required.
The composite material is composed of carbon fiber and epoxy resins. Now, density is an intensive unit. So, to approach this problem, let's assume there is 1 gram of composite material. Thus, mass carbon + mass epoxy = 1 g.
Volume of composite material = 1 g / 1.615 g/cm³ = 0.619 cm³
Volume of carbon fibers = x g / 1.74 g/cm³
Volume of epoxy resin = (1 - x) g / 1.21 g/cm³
a.) V of composite = V of carbon fibers + V of epoxy resin
0.619 = x/1.74 + (1-x)/1.21
Solve for x,
x = 0.824 g carbon fibers
1-x = 0.176 g epoxy resins
Vol % of carbon fibers = [(0.824/1.74) ÷ 0.619]*100 =<em> 76.5%</em>
b.) Weight % of epoxy = 0.176 g epoxy/1 g composite * 100 = <em>17.6%</em>
Weight % of carbon fibers = 0.824 g carbon/1 g composite * 100 = <em>82.4%</em>
