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VladimirAG [237]
3 years ago
8

4. Does an atom of an element always have the same number of neutrons as other atoms of the same

Chemistry
1 answer:
Sergeeva-Olga [200]3 years ago
6 0

Explanation:

No. Isotopes are atoms of the same element with different atomic masses (due to the different number of neutrons)

For example, carbon exists as carbon-12 and carbon-14, which both have 6 protons but have 6 and 8 neutrons respectively.

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In the early twentieth century, what was Alexander Fleming’s hypothesis concerning the relationship between a yellow-green mold
SpyIntel [72]

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>

4 0
3 years ago
Match the following.
cupoosta [38]
1.icosahedralb2.helicalc3.complexa
8 0
3 years ago
3. Which change of state involves adding thermal energy to a substance!
MakcuM [25]

Answer:

A) Melting

Explanation:

The three changes of phase described in this problem are:

  • Melting: melting occurs when a substance in solid state turns into liquid state. Since molecules in liquid state have more energy than molecules in solid state (because in liquids, molecules can slide past each other, while in solids they can't move, but only vibrate), thermal energy must be added in order to melt a substance
  • Freezing: freezing occurs when a liquid substance turns into solid state (the opposite of melting). Since molecules in liquid state have more energy than molecules in solid state, thermal energy must be removed from the substance in order to cause freezing
  • Condensation: condensation occurs when a gaseous substance turns into liquid state. Since molecules in gaseous state have more energy than molecules in liquid state, thermal energy must be removed from the substance in order to cause condensation

So the correct option is

A) melting

5 0
3 years ago
25.0 ml of a 6.0 m hno3 stock solution is diluted using water to 100 ml. How many moles of hno3 are present in the dilute soluti
lana66690 [7]

Answer:

The answer to your question is: 6 moles of HNO₃

Explanation:

Data

Volume = 25 ml

Concentration = 6 M HNO₃

Diluted 100 ml

Formula

Molarity = # moles / volume

# of moles = Volume x Molarity

Process

# of moles = 0.10 x 6

                 = 6 moles

6 0
3 years ago
Read 2 more answers
A mole of X reacts at a constant pressure of 43.0 atm via the reaction
liberstina [14]
Below is the solution:

<span>-62.0 kJ ΔH = -75.0 kJ, P = 43.0 atm 43atm x 101325 Pa/1 atm = 4356975 Pa or N/m2 ΔV = 2.0 L - 5.0 L = 3.0 L = -3.0 x 10-3 m3 w = -PΔV = -(4356975 N/m2) (-3.0 x 10-3 m3) = 13070 N m = 13070 J = 13.07 kJ At constant P, q = ΔH = -75.0 kJ & ΔE = q + w = - 75.0 kJ + 13.07 kJ = -61.93 kJ = -62.0 kJ</span>
5 0
3 years ago
Read 2 more answers
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