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1 year ago

What is responsible for the differences in chemical shift observed in carbon 4 in 4-fluoroheptane and carbon 4 in heptane?

1 answer:

4 0

The chemical shift of a given proton is decided specifically with the aid of interactions with the nearby electrons. The most necessary thing to recognize is that when electrons are subjected to an external magnetic field, they structure their own small prompted magnetic fields in opposition to the exterior field.

Consider the methane molecule ( CH4 ) in which the four equal protons have a chemical shift of 0.23 ppm (this is a price we can look up in any chemistry reference source). The valence electrons around the methyl carbon, when subjected to B0, generate their own very small triggered magnetic area that opposes B0 . This induced field, to a small however full-size degree, shields the close by protons from experiencing the full force of B0 , an impact regarded as local diamagnetic shielding. In different words, the methane protons do now not quite journey the full force of B0 - what they journey is known as Beff , or the high-quality field, which is slightly weaker than B0 due to the have an effect on of the close by electrons.

In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of an atomic nucleus relative to a preferred in a magnetic field. Often the position and range of chemical shifts are diagnostic of the shape of a molecule.

Learn more about chemical shifts here:

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2 years ago

6. The graph below shows the heating curve for ethanol (from –200C to 150C). Calculate the amount of heat (kJ) required for each

Kazeer [188]

This problem is providing the heating curve of ethanol showing relevant data such as the initial and final temperature, melting and boiling points, enthalpies of fusion and vaporization and specific heat of solid, liquid and gaseous ethanol, so that the overall heat is required and found to be 1.758 kJ according to:

<h3>Heating curves:</h3>

In chemistry, we widely use heating curves in order to figure out the required heat to take a substance from a temperature to another. This process may involve sensible heat and latent heat, when increasing or decreasing the temperature and changing the phase, respectively.

Thus, since ethanol starts off solid and end up being a vapor, we will find five types of heat, three of them related to the heating-up of ethanol, firstly solid, next liquid and then vapor, and the other two to its fusion and vaporization as shown below:

$Q_T=Q_1+Q_2+Q_3+Q_4+Q_5$

Hence, we begin by calculating each heat as follows, considering 1 g of ethanol is equivalent to 0.0217 mol:

$Q_1=0.0217mol*111.5\frac{J}{mol*\°C}[(-114.1\°C)-(-200\°C)] *\frac{1kJ}{1000J} =0.208kJ\\
\\
Q_2=0.0217mol*4.9\frac{kJ}{mol} =0.106kJ\\
\\
Q_3=0.0217mol*112.4\frac{J}{mol*\°C}[(78.4\°C)-(-114.1\°C)] *\frac{1kJ}{1000J} =0.470kJ\\
\\
Q_4=0.0217mol*38.6\frac{kJ}{mol} =0.838kJ\\
\\
Q_5=0.0217mol*87.5\frac{J}{mol*\°C}[(150\°C)-(78.4\°C)] *\frac{1kJ}{1000J} =0.136kJ$

Finally, we add them up to get the result:

$Q_T=0.208kJ+0.106kJ+0.470kJ+0.838kJ+0.136kJ\\
\\
Q_T=1.758kJ$

Learn more about heating curves: brainly.com/question/10481356

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2 years ago

How does carbonic acid work to maintain blood pH? (Select all that apply.) Check All That Apply When blood is too basic, carboni

Vlad1618 [11]

Answer:

When blood is too basic, carbonic acid can ionize to bicarbonate and H+ ions, adding H+ ions to the blood.

When blood becomes too acidic, bicarbonate combines with extra H+ ions to form carbonic acid, removing H+ ions from the blood.

Carbonic acid can raise or lower the pH of blood.

Explanation:

A buffer is a solution that resists changes to its pH when small quantities of acids or bases are added to it. The human blood serves as a buffer as it contains a buffer of carbonic acid (H2CO3) and bicarbonate anion (HCO3-) which serves to maintain blood pH between 7.35 and 7.45. Other buffering systems in blood exist such as the Hydrogen ion and oxygen gas which affects oxygen binding to haemoglobin, however the carbonic-acid-bicarbonate buffer is the most important buffer for maintaining acid-base balance in the blood.

A buffer solution is made up of an acid and its conjugate base or a base and its conjugate acid. For carbonic acid-bicarbonate buffer, carbonic acid serves as the acid while bicarbonate serves as the base. When a little quantity of a base as hydroxide ions is added to a buffer, the acid reacts with it and remove it from the solution. On the other hand, when a little quantity of an acid as hydrogen ions are added to a buffer, the conjugate base reacts with it and remove it from the solution, thus keeping the pH of the solution fairly constant.

In the carbonic acid-bicarbonate buffer:

When blood is too basic, carbonic acid can ionize to bicarbonate and H+ ions, adding H+ ions to the blood.

When blood becomes too acidic, bicarbonate combines with extra H+ ions to form carbonic acid, removing H+ ions from the blood.

Thus, carbonic acid can raise or lower the pH of blood.

3 0

3 years ago