Answer:
Hint As we know that the concept of mole is mainly to calculate the entities at the microscopic level that is ions, particles, molecules, electrons or atoms etc. It is found that mole is having the symbol mol.
Complete Step by step solution:
- As we are being provided with the information that there is 15 grams of lithium. As we know that the molar mass of lithium is 6.94 g/mol.
- As we know that mole is the amount of substance that has entities as there are atoms exactly in 12 g of carbon isotope. We should note that the number of entities in one mole is important because it is called the Avogadro constant. The numeric value of this constant is 6.022×1023.
- Firstly we will write the given mass as:
156.022×1023
- Now, we can find the number of moles by the formula of moles that is given mass of the substance divided by the molar mass of the substance.
moles=given massmolar mass⟹156.022×10236.94⟹15×6.946.022×1023⟹17.28×10−23moles
- Hence, we can conclude that there are 17.28×1023 moles in 15 grams of lithium.
Note:
- If we want to calculate the number of moles of an individual entity, like say A, that is dissolved in a solution of an entity say B (A+B), then we can do so by using the concept of mole fraction. The formula of mole fraction is given as moles of a substance divided by the total number of moles.
- We should not forget to write the unit after solving the solution. Explanation:
The boiling point of a solution of 6.4 g of vanillin in 50.0g of ethanol is 77.47 degree C.
Change in boiling point of solution
ΔTb = (Kb)(m), where
ΔTb = change in temperature
Kb = elevation constant = 1.22 °C./m
m = molality of the solution
Following the calculation of the moles of vanillin, the molality of vanillin in ethanol will be determined..
Moles of vanillin = 6.4g / 152.12g/mol = 0.042 mol
m of vanillin = 0.042mol / 0.05kg = 0.84m
putting all values on the above equation,
ΔTb = (1.22)(0.84) = 1.0248 °C.
Given;
boiling point of ethanol = 78.5 °C.
So the boiling point of vanillin = 78.5 - 1.0248 = 77.47 °C
Hence, the boiling point of a solution of vanillin is 77.47 °C.
Learn more about the boiling point with the help of the given link:
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the basic unit of distance is the centimeter (cm) There are 100 centimeters in a meter and 1000 meters in a kilometer.
Answer: gamma& the firt one
Explanation:
The cyclo-heptatrienyl anion will be considered as antiaromatic compound.
A cyclic compound with a greater energy electron system due to the existence of a 4n delocalized electron is what makes up an anti-aromatic chemical.
Due to its eight pi electrons, the cycloheptatrienyl anion (also known as the tropylium anion) should be antiaromatic; yet, the extra lone pair on one carbon could enable that carbon to become
hybridized, placing the extra electrons in an
orbital. It would become non-planar as well as non-aromatic as a result.
Therefore, the cyclo-heptatrienyl anion will be considered as antiaromatic compound.
To know more about antiaromatic compound.
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