How does Dr.Hoffmann's ultrasound device benefit society? ( modern chemistry textbook page 180).

2 answers:

7 0

She developed new models for emergency ultrasound education and competency assessment, created a successful emergency ultrasound fellowship program, and introduced electronic workflow solutions to Hopkins, increasing the use of emergency ultrasound by 7-fold.

Karo-lina-s [1.5K]3 years ago

7 0

Answer:

In 1966, Dr. Hoffmann recorded for the first time in medicine embryonic movements and the heartbeat of the fetus using an ultrasound system.

Explanation:

Today, ultrasound is a technique widely used by many medical specialties, in the emergency department, in intensive care or in daily practice.

In 1794, the Italian Spallanzani observed that during the flight of bats they did not collide with anything despite being blind. It is then that he theorizes that they emitted sounds imperceptible to the man he would call ultrasounds, which they capture with their ears after bouncing off objects.

In 1842, Christian Doppler's first article on the effect of his name appears.

In 1912, Richardson suggests the use of ultrasonic echoes to detect submerged objects, creating the first ultrasonic generator five years later by Paul Langevin and Chilowsky.

Since then the applications of this new technology have been unstoppable, especially in medicine.

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Is selenium tetrafluoride an ionic or covalent bond?

nasty-shy [4]

Answer:

Synthesis

The first reported synthesis of selenium tetrafluoride was by Paul Lebeau in 1907, who treated selenium with fluorine:[1]

Se + 2 F2 → SeF4

A synthesis involving more easily handled reagents entails the fluorination of selenium dioxide with sulfur tetrafluoride:[2]

SF4 + SeO2 → SeF4 + SO2

An intermediate in this reaction is seleninyl fluoride (SeOF2).

Other methods of preparation include fluorinating elemental selenium with chlorine trifluoride:

3 Se + 4 ClF3 → 3 SeF4 + 2 Cl2

Structure and bonding

Selenium in SeF4 has an oxidation state of +4. Its shape in the gaseous phase is similar to that of SF4, having a see-saw shape. VSEPR theory predicts a pseudo-trigonal pyramidal disposition of the five electron pairs around the selenium atom. The axial Se-F bonds are 177 pm with an F-Se-F bond angle of 169.2°. The two other fluorine atoms are attached by shorter bonds (168 pm), with an F-Se-F bond angle of 100.6°. In solution at low concentrations this monomeric structure predominates, but at higher concentrations evidence suggests weak association between SeF4 molecules leading to a distorted octahedral coordination around the selenium atom. In the solid the selenium center also has a distorted octahedral environment.

Reactions

In HF, SeF4 behaves as a weak base, weaker than sulfur tetrafluoride, SF4 (Kb= 2 X 10−2):

SeF4 + HF → SeF3+ + HF2−; (Kb = 4 X 10−4)

Ionic adducts containing the SeF3+ cation are formed with SbF5, AsF5, NbF5, TaF5, and BF3.[3] With caesium fluoride, CsF, the SeF5− anion is formed, which has a square pyramidal structure similar to the isoelectronic chlorine pentafluoride, ClF5 and bromine pentafluoride, BrF5.[4] With 1,1,3,3,5,5-hexamethylpiperidinium fluoride or 1,2-dimethylpropyltrimethylammonium fluoride, the SeF62− anion is formed. This has a distorted octahedral shape which contrasts to the regular octahedral shape of the analogous SeCl62−. [5]

Explanation:

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3 years ago

What is the concentration of hydronium ions and hydroxide ions

nikdorinn [45]

To find the concentration of hydronium ions, take 10 raised to the negative pH:
10^-9.56= 2.75 x10^-10M

To find the concentration of hydroxide ions, take 10 raised to the negative pOH: 10^-4.44 = 3.63 x10^-5M

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3 years ago

Determine the bonding type for boron trihydride given the electronegativity on the Pauling scale for boron is 2.0 and for hydrog

Anika [276]

Answer: The bond between boron and hydrogen in boron trihydride is covalent bond.

Explanation:

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