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3 years ago

What is the molecular formula of a hydrocarbon with m+ = 78?

Chemistry

1 answer:

fiasKO [112]3 years ago

4 0

A molecular formula represents the exact number of atoms present for each element in the compound.

For carbon atom: $\frac{78}{12}$ = $6\frac{6}{12}$ ( as molar mass of carbon is 12 g/mol)

Now, 6 carbon atoms are present and rest are hydrogen atoms i.e. 6

Thus, formula becomes $C_{6}H_{6}$ ( $C_{x}H_{y})$

Now, check for unsaturation:

Degree of unsaturation = $\frac{2x+2-y}{2}$

Substitute the value of x and y,

Degree of unsaturation = $\frac{2(6)+2-6}{2}$

= $\frac{12-4}{2}$

= $4$ implies one ring and three double bonds.

Thus, formula comes out to be $C_{6}H_{6}$ i.e. benzene ring.

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In a two-step synthesis, C6H11Br is converted into C6H12O. From the structure of the product, molecular formula of the starting

tamaranim1 [39]

Answer:

See explanation below

Explanation:

The question is incomplete. However in picture 1, you have the starting materials and the structure of the product, which you miss in this part.

Now, in picture 2, you have the starting reactant and the product, and the mechanism that is taking place here.

First, all what we have here is an acid base reaction. In the first step, we are using the acid medium to convert the reactant into an alcohol. The bromine there, is not leaving the molecule yet, because it's neccesary for the next step. The starting reactant is an alkene, in that way, we can convert the reactant in the first step into a secondary alcohol. In other words, the first reaction is a alkene hydration.

In the second step, we use a strong base. You may say this is a strong nucleophile and will do a Sn2 reaction to form another alcohol there, but it's not the case, because, before any kind of reaction happens, the priority here is always the acid base, so the base will react with the acidic hydrogen. In this case, it will substract an hydrogen from the OH. When this happens, the lone pair will do an auto condensation here, and attacks the bromine in the molecule. In this way, the molecule will become a cyclomolecule, and that way it form the final product.

See picture 2, for mechanism

8 0

3 years ago

Without doing any calculations, match the following thermodynamic properties with their appropriate numerical sign for the follo

siniylev [52]

Answer:

∆H > 0

∆Srxn <0

∆G >0

∆Suniverse <0

Explanation:

We are informed that the reaction is endothermic. An endothermic reaction is one in which energy is absorbed hence ∆H is positive at all temperatures.

Similarly, absorption of energy leads to a decrease in entropy of the reaction system. Hence the change in entropy of the reaction ∆Sreaction is negative at all temperatures.

The change in free energy for the reaction is positive at all temperatures since ∆S reaction is negative then from ∆G= ∆H - T∆S, we see that given the positive value of ∆H, ∆G must always return a positive value at all temperatures.

Since entropy of the surrounding= - ∆H/T, given that ∆H is positive, ∆S surrounding will be negative at all temperatures. This is so because an endothermic reaction causes the surrounding to cool down.

3 0

3 years ago

An element has two naturally-occurring isotopes. The mass numbers of these isotopes are 113 amu and 115 amu, with natural abunda

DENIUS [597]

Answer: Its average atomic mass is 114.9 amu

Explanation:

Mass of isotope 1 = 113 amu

% abundance of isotope 1 = 5% = $\frac{5}{100}=0.05$