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Vera_Pavlovna [14]
3 years ago
8

Помогите срочно сделать по химии промежуточную отестацию за 8 класс

Chemistry
1 answer:
il63 [147K]3 years ago
6 0

Answer:

This is site for English  speakers.  Этот сайт на английском, поэтому вопрос могут удалить

Explanation:

1. 2)

2. 3)

3. 4) Sr

4. 3)

5. 4)

6. 2)

7. 1)

8. 4)

9. 3)

10. 3)

11. SO3, H2SO4, Na2SO4

12.

A) оксид меди (II) 2) CuO

Б) хлорид меди(II) 4) CuCl2

В) сульфит меди (II) 3) CuSO 3

Г) гидроксид меди (II) 1) Cu(OH)2

13.

1. Fe+HCl= б) FeCl 2 +H 2

2.Fe+O2= в) Fe 3 O 4

3. Fe(OH) 3  = г)Fe 2 O 3 +H 2O

4. FeCl 2 +NaOH= а) Fe(OH) 2 +NaCl

14. 2Ca + O2 = 2CaO

CaO + H2O = Ca(OH)2

Ca(OH)2 + 2HCl = CaCl2 + 2H2O

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A sample can not be broken down physically or chemically what is it
KIM [24]

Answer:

Pure Substance. A sample of matter, either a single element or a single compound, that has definite chemical and physical properties. Element. A pure substance that cannot be broken down into other substances by chemical or physical means.

Explanation:

Sorry if it's wrong!!!!!!!

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3 years ago
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Are solar and lunar eclipses processed by the movements of the Earth and moon?
Inga [223]

Explanation:

As the Earth rotates on its axis and revolves around the Sun, several different effects are produced. When the new moon comes between the Earth and the Sun along the ecliptic, a solar eclipse is produced. When the Earth comes between the full moon and the Sun along the ecliptic, a lunar eclipse occurs.

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2 years ago
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most radioactive atoms “spontaneously” decay to a more stable form. where does the “additional” energy go once the atoms have de
blsea [12.9K]

When most radioactive atoms “spontaneously” decay to a more stable form the “additional” energy is converted to radiation with the emission of radioactive particles.

<h3>What is radioactivity?</h3>

Radioactivity is the spontaneous decay of the nucleus of an atom with the emission of radiation and nuclear particles.

Elements that spontaneously decay are called radioactive elements.

When these radioactive elements decay, they form more stable isotopes or elements.

The spontaneous decay of atoms of radioactive elements is in order for the nucleus of the atom to become stable and non-radioactive.

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4 0
8 months ago
What is the kinetic energy of the emitted electrons when cesium is exposed to UV rays of frequency 1.3×1015Hz?
Sonja [21]

Answer:

We know that

ħf = ф + Ekmax  

where  

ħ = planks constant = 6.626x10^-34 J s  

f = frequency of incident light = 1.3x10^15 /s (1 Hz =

1/s)

ф = work function of the cesium = 2.14 eV  

Ekmax = max  kinetic energy of the emmitted electron.  

We distinguish that:

1 eV = 1.602x10^-19 J

So:

2.14 eV x (1.602x10^-19 J / 1 eV) = 3.428x10^-19 J

So,

Ekmax = (6.626x10^-34 J s) x (1.3x10^15 / s) - 3.428x10^-19 J

= 8.6138x10^-19 J - 3.428x10^-19 J = 5.1858x10^-19 J  

Answer:

5.19x10^-19 J  

Kinetic energy:

In physics, the kinetic energy of an object is the energy that it owns due to its motion. It is defined as the work required accelerating a body of a given mass from rest to its specified velocity. Having expanded this energy during its acceleration, the body upholds this kinetic energy lest its speed changes.

Answer details:

Subject: Chemistry

Level: College

Keywords:

• Energy  

• Kinetic energy

• Kinetic energy of emitted electrons

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What main criterion determines major divisions in the geologic time scale?
koban [17]

The answer is B. the occurrence of huge events in Earth's natural history

The geologic time scale is a system of chronological dating that relates geological strata to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history.

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