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antoniya [11.8K]
3 years ago
10

Which of the following statements is true of vibrations? A. The frequency of infrasonic vibrations is much too high to be heard

by humans. B. Infrasonic vibrations are used in sonar equipment and to detect flaws in steel castings. C. Ultrasonic vibrations have a frequency lower than the range for normal hearing. D. Neither ultrasonic nor infrasonic vibrations can be heard by humans
Chemistry
2 answers:
Wewaii [24]3 years ago
4 0

D. ( Neither ultrasonic nor infrasonic vibrations can be heard by humans. )

Ilia_Sergeevich [38]3 years ago
4 0

Answer:

The correct statement is option D, that is, neither ultrasonic nor infrasonic vibrations can be heard by humans.

Explanation:

The ultrasonic vibrations are the sound waves exhibiting the frequency of more than 20000 Hz, whereas the upper-frequency limit in human beings is about 20 Hz. Humans cannot hear the ultrasound as it is more than 20 Hz.  

On the other hand, the infrasonic vibrations refer to a low-frequency sound, it is lower in frequency in comparison to 20 Hz, that is, the usual limit of human hearing. Thus, for humans to perceive infrasound, the pressure of the sound must be adequately high.  

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Give 3 safety measures in handling acids or basic
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8 0
3 years ago
Different of an element have different numbers of neutrons.
inna [77]

Answer:

Isotopes  

Explanation:

This is the definition of isotopes: they are atoms of the same element that contain different numbers of neutrons.

4 0
4 years ago
Which electron configuration is correct for a sodium ion?
jeka94

The electron configuration for sodium ion Na⁺ : <u>(2) 2-8</u>

<h3>Further explanation </h3>

In an atom there are levels of energy in the shell and sub shell

This energy level is expressed in the form of electron configurations.

Writing electron configurations starts from the lowest to the highest sub-shell energy level. There are 4 sub-shells in the shell of an atom, namely s, p, d and f. The maximum number of electrons for each sub shell is

  • s: 2 electrons
  • p: 6 electrons
  • d: 10 electrons and
  • f: 14 electrons

Charging electrons in the sub shell uses the following sequence:

<em>1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², etc. </em>

Determination of electron configurations based on principles:

• 1. Aufbau: Electrons occupy orbitals of the lowest energy level

• 2 Hund: electrons fill orbitals with the same energy level

• 3. Pauli: no electrons have the same 4 quantum numbers

The alkali metal Na will release electrons to form Na + so that the electron configuration is stable as the noble gas element Ne

electron configuration Ne: [He] 2s² 2p⁶

Na electron configuration: [Ne] 3s¹

electron configuration Na + = [Ne] = [He] 2s² 2p⁶

The maximum number of electrons in the shell K, L, M, N

According to Bohr, the maximum number of electrons that can occupy each atomic shell can be calculated by the formula 2n²

  • K shell (n = 1): 2.1² = 2 electrons
  • L shell (n = 2): 2. 2² = 8 electrons
  • M shell (n = 3): 2. 3² = 18 electrons
  • N shell (n = 4): 2. 4² = 32 electrons

If we look at the configuration of the Na⁺ ion:

1s² 2s² 2p⁶ then

on the shell n=1 (1s) there are 2 electrons

on the shells n=2 (2s and 2p) there are 8 electrons

So that the configuration

Na⁺ = 2-8

<h3>Learn more </h3>

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Gelneren [198K]

Answer:

a. [Na₂CrO₄] = 0.10 M

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Explanation:

Molarity means a sort of concentration which indicates the moles of solute over 1L of solution.

We determine the moles of solute: 12.5 g / 162g/mol = 0.0771 moles

We convert the volume of solution from mL to L = 750 mL . 1L/1000mL = 0.750L

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Then, Molarity . Volume of solution (L) = moles of solute

We convert the volume of solution from mL to L = 150 mL . 1L/1000mL = 0.150L

0.112 mol/L . 0.150L = Moles of solute → 0.017 moles of KBr

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4 years ago
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If an acid is splashed on your skin, wash at once with
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D. plenty of water

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