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True [87]
3 years ago
6

In the early twentieth century, what was Alexander Fleming’s hypothesis concerning the relationship between a yellow-green mold

and certain strains of bacteria?
a. He thought the bacteria had released a chemical that caused the mold to grow. b.He thought the bacteria fed on the mold, causing it to shrink and disappear.
c. He thought the mold had released a chemical that prevented the bacteria’s growth.
Chemistry
1 answer:
SpyIntel [72]3 years ago
4 0

Answer:

The correct answer is the option c)He thought the mold had released a chemical that prevented the bacteria’s growth.

Explanation:

In the 1920s, Alexander Fleming was working in his laboratory at St. Mary's Hospital in London when, almost by accident, he discovered a naturally growing substance that could attack certain bacteria. In one of his experiments, Fleming observed that colonies of a bacterium had been depleted or removed by a mold that grew on the same Petri dish. He observed that the bacteria furthest from the fungus had grown to produce large-sized colonies, while the colonies closest to the fungus were tiny. He determined that mold made a substance that could dissolve bacteria. The fungus was penicilium chrysogenum and thus Fleming called this substance penicillin, by the name of the mold that produces it. Thus, after several years of experiments in 1930, Howard Florey and Ernest Chain developed at Oxford University the procedures to produce pure penicillin from the fungus that Fleming isolated. Thus penicillin could be concentrated by Florey and Chain, and in 1945 they shared with Fleming the Nobel Prize in Medicine.

Then, <u><em>the correct answer is the option c)He thought the mold had released a chemical that prevented the bacteria’s growth.</em></u>

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The potential difference across the terminals of a battery of e.m.f. 12 V and internal resistance 2 ohm drops to 10 V when it is
lesantik [10]

Explanation:

The given data is as follows.

      E.m.f = 12 V,        Voltage = 10 V,        Resistance = 2 ohm

Hence, calculate the current as follows.

          I = \frac{E - V_{t}}{r_{int}}

Putting the given values into the above formula as follows.

         I = \frac{E - V_{t}}{r_{int}}

           = \frac{12 - 10}{2}

           = 1 A

Atomic weight of copper is 63.54 g/mol. Therefore, equivalent weight of copper is \frac{M}{2}.

That is,          \frac{M}{2}

                = \frac{63.54 g/mol}{2}

Hence, electrochemical equivalent of copper is as follows.

                   Z = (\frac{E}{96500}) g/C

                       = (\frac{63.54 g/mol}{2 \times 96500}) g/C

                       = 3.29 \times 10^{-4} g/C

Therefore, charge delivered from the battery in half-hour is calculated as follows.

                     It = Q

                       = 1 \times \frac{1}{2} \times 60 times 60  

                       = 1800 C

So, copper deposited at the cathode in half-an-hour is as follows.

                     M = ZQ

                = 3.29 \times 10^{-4} g/C \times 1800 C

                = 0.5927 g

Thus, we can conclude that 0.5927 g of copper is deposited at the cathode in half an hour.

8 0
3 years ago
You turn on your gas fireplace at home and wonder why you don't immediately feel the
DENIUS [597]

Answer:

the (air) atmosphere

Explanation:

it fast go to the atmosphere

8 0
3 years ago
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Quantum numbers arise naturally from the mathematics used to describe the possible states of an electron in an atom. The four qu
ad-work [718]

Answer:

The allowable values for the principle quantum number (n) are integers greater than zero.

The allowable values for the angular momentum quantum number (l) are integers from 0 to n-1.

The allowable values for the magnetic quantum number (ml) are integers from -l to l.

The allowable values for the spin quantum number (ms) are -1/2 and 1/2.

Explanation:

<em>Identify allowable combinations of quantum numbers for an electron. Select all that apply.</em>

  • <em>The allowable values for the principle quantum number (n) are integers greater than zero. </em>TRUE. The principal quantum number (n) represents the level of energy in which an electron is and can take positive integer values.
  • <em>The allowable values for the angular momentum quantum number (l) are integers from 0 to n-1.</em> TRUE. The angular quantum number (l) represents the sublevel of energy and the kind of orbital an electron is in and can take integer values from 0 to n-1. For instance, if n = 1, l can take the value "0", which represents the sublevel and orbital "s".
  • <em>The allowable values for the magnetic quantum number (ml) are integers from -l to l.</em> TRUE. The magnetic quantum number (ml) represents the orientation of an orbital in space and can take integers values from -l to +l. For instance, if l = 1 (p orbital), ml can take the values -1, 0 and 1, which refer to orbitals px, py and pz.
  • <em>The allowable values for the spin quantum number (ms) are -1/2 and 1/2. </em>TRUE. The spin quantum number (ms) represents the spin of the electron and can take values -1/2 and +1/2.
5 0
4 years ago
Calculate the cell potential, E, for the following reactions at 26.29 °C using the ion concentrations provided. Then, determine
yanalaym [24]

Answer:

I will work only one of the listed equations ... you follow the given example for the remaining reactions. Thank you :-)

Rxn 1: Pt°(s) + Fe⁺²(aq) ⇄ Pt⁺²(aq) + Fe°(s)

a) E(Pt⁺²/Fe°) = - 1.668v

b) Process is Non-spontaneous if E(cell) < 0

Explanation:

Pt°(s) + Fe⁺²(aq) ⇄ Pt⁺²(aq) + Fe°(s) ⇔

Pt°(s)|Pt⁺²[0.057M]║Fe⁺²[0.006M]|Fe°(s)

As written, Pt° is shown undergoing oxidation with Fe⁺² undergoing reduction. Applying the reduction potentials to the analytical equations for E(cell) and ΔG(cell) gives E(Pt/Fe⁺²) < 0 and ΔG(Pt/Fe⁺²) > 0 which indicate a non-spontaneous process. The following supports this conclusion.

E°(Fe⁺²) = -0.44v

E°(Pt⁺²) = +1.20v

E°(Pt/Fe⁺²) =E°(Redn) - E°(Oxidn) =E°(Fe⁺²) - E°(Pt⁺²)

= -0.44v - (+1.20v) = - 1.64v

[Fe⁺²] = 0.0066M

[Pt⁺²] = 0.057M

n = electrons transferred = 2

E(nonstd) = E°(std) - (0.0592/n)logQ);

Q = [Pt⁺²]/[Fe⁺²]

= -1.64v - (0.0592/2)log[0.057M]/[0.006M]v = -1.668v

Also, if ΔG(cell) > 0 => indicates non-spontaneous process

ΔG(Pt/Fe⁺²) = - nFE = -(2)(96,500Coulombs)((-1.664v) > 0 Kj => nonspontaneous rxn. (1 Coulomb-volt = 1 Kilojoule)

7 0
3 years ago
Provide an explanation that is grounded in polarity that better explains why oil is not miscible in vinegar.
butalik [34]

Explanation:

Vinegar is a sour liquid made up of acetic acid compounds. Oil is a complex non-polar chemical compound with a high amount of hydrogen and carbon in its structure.

  • Vinegar is a polar acid, although a weak one.
  • Generally, for a substance to mix with another one, they must be similar.
  • Solubility of compounds controls miscibility.
  • When two substances are miscible, they can be said to be soluble in one another.
  • In solubility, like substances dissolves like substances.
  • This implies that polar compounds will only dissolve polar compounds.
  • Non-polar compounds will only dissolve in non-polar solvents.
  • Since vinegar is polar and oil is non-polar, they will not dissolve one another.

Learn more:

Polarity brainly.com/question/2615067

#learnwithBrainly

4 0
3 years ago
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