What sign of chemical change occurs during chemiluminesence?
Production of heat
Production of a gas
Production of light
O Production of a solid (precipitation)

Answer:

They want to know how long it has been since it last erupted.

Explanation:

Scientists study a volcano's history to try to predict when it will next erupt.  They also want to know the time span between its previous eruptions

Answer:

27)

a. Silver nitrate

b. Lead chromate

c. Anhydrous magnesium acetate

d. Copper nitrate

28) a. KNo3

Answer:

methanol because it is liquid at room temperature which means that it melts at a lower temperature

Silicon dioxide is a solid at room temperature and methanol is a liquid. Silicon dioxide has a higher melting point than methanol because silicon dioxide is solid, and with increasing temperature, it will melt.

Melting point is that point or temperature at which the solid items are converted into liquid, and it changes their atoms and the atoms lose their compactness.

Here, two compounds are given, Silicon dioxide and methanol, the first one is solid at room temperature, so it will need more temperature to melt down and methanol is still liquid at room temperature, so its melting point is low.

Thus, methanol is a liquid while silicon dioxide is a solid at ambient temperature. Because silicon dioxide is a solid and melts at greater temperatures, it has a higher melting point than methanol.

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Cobalt-60 is comprised of 27 protons, 33 neutrons, and 27 electrons. Nuclear reactors are used to artificially create it.

A radioactive isotope containing cobalt with something like a half-life of 5.2713 centuries is called cobalt-60 (60Co). Nuclear reactors are used to artificially create it. Neutron irradiation of bulk material of the monoisotopic as well as mononuclidic cobalt element 59 Co is necessary for deliberate industrial manufacture.

The accidentally generated 60 Co in the latter instance (inside the absence of additional cobalt) is mostly the product of many phases involving neutron activation on iron isotopes inside the reactor. Cobalt-60 is comprised of 27 protons, 33 neutrons, and 27 electrons.

Therefore,  cobalt-60 is comprised of 27 protons, 33 neutrons, and 27 electrons.

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Answer:

[Ar] 4s²

Explanation:

The full electron configuration for the Ca+ ion is:

1s² 2s² 2p⁶ 3s² 3p⁶.

To determine the full electron configuration for a Ca+ ion, we need to remove one electron from the neutral calcium atom (Ca). The neutral calcium atom has the electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

When Ca loses one electron to form the Ca+ ion, the electron removed comes from the highest energy level, which is the 4s orbital.

Therefore, the full electron configuration for the Ca+ ion is:

1s² 2s² 2p⁶ 3s² 3p⁶.

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Answer:

The Lewis structure for XeF4 has a total of 36 valence electrons. When we are done adding valence electrons we check each atom to see if it has an octet (full outer shell). We also need to check to make sure we only used the number of available valence electrons we calculated earlier (no more, no less).

Explanation:

I CANT DELETE THE ANSWER, SO HERE.

Answer:

24.9

Explanation:

-

Answer:

Seven methods were used to assess water quality in the river system. These methods included single-factor assessment, water quality grading, comprehensive pollution index, the Nemerow pollution index, principle component analysis, fuzzy comprehensive evaluation, and comprehensive water quality identification index.

The reaction Pb(NO3)2(aq) + NiCl2(aq)---------> PbCl2(s) + Ni(NO3)2(aq) is a precipitation reaction.

A chemical reaction is said to occur when two or more substances are combined to produce new substances. Chemical reactions are classified based on the kind of change taking place in the reaction.

In the reaction;

Pb(NO3)2(aq) + NiCl2(aq)---------> PbCl2(s) + Ni(NO3)2(aq)

We can see that a solid is formed when lead II nitrate reacts with nickel II chloride. This is a precipitation reaction.

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Using Charles law

[tex]\\ \sf\longmapsto V_1T_2=V_2T_1[/tex]

[tex]\\ \sf\longmapsto V_2=V_1T_2\div T_1[/tex]

[tex]\\ \sf\longmapsto V_2=\dfrac{49.8(356)}{291}[/tex]

[tex]\\ \sf\longmapsto V_2=\dfrac{17728.8}{291}[/tex]

[tex]\\ \sf\longmapsto V_2=60.9mL[/tex]

We want to find the concentration of the resulting solution of mixing 35mL of a given solution and 0.225 L of water.

We will find that the concentration is 13.5%.

First, we need to write both of these in the same units.

We know that:

1000 mL = 1L

Then:

35 mL = 0.035 L

So when we mix the solution and the water we end with a total volume of:

V = 0.035L + 0.225L = 0.260L

The concentration of solution will be equal to the quotient between the volume of solution we used (0.035 L) and the total volume of the mixture (0.260L)

We will get:

Concentration = (0.035L)/(0.260L) = 0.135

Now to write it as a percentage, we only need to multiply this by 100%.

0.135*100% = 13.5%

This means that the mixture has a concentration of the 13.5%.

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The mass in grams of 3.011 x 10²³ atoms of F is 9.5 g.

The mass in grams of  1.50 x 10²³ atoms of Mg is 5.98 g.

The mass in grams of  4.50 x 10¹² atoms of Cl is 2.65 x 10⁻¹⁰ g.

The mass in grams of  8.42 x 10¹⁸ atoms of Br is 1.12 x 10⁻³ g.

The mass in grams of  25 atoms of W is 3.1 x 10⁻²¹ g.

The mass in grams of  1 atom of Au is 3.27 x 10⁻²² g.

The mass in grams of 3.011 x 10²³ atoms of F is calculated as follows;

6.023 x 10²³ atoms = 19 g of F

3.011 x 10²³ atoms F  = ?

= (3.011 x 10²³ x 19 g)/(6.023 x 10²³)

= 9.5 g

The mass in grams of  1.50 x 10²³ atoms of Mg is calculated as follows;

6.023 x 10²³ atoms = 24g of Mg

1.5 x 10²³ atoms F  = ?

= (1.5 x 10²³ x 24 g)/(6.023 x 10²³)

= 5.98 g

The mass in grams of  4.50 x 10¹² atoms of Cl is calculated as follows;

6.023 x 10²³ atoms = 35.5 g of Cl

4.5 x 10²³ atoms Cl  = ?

= (4.5 x 10¹² x 35.5 g)/(6.023 x 10²³)

= 2.65 x 10⁻¹⁰ g

The mass in grams of  8.42 x 10¹⁸ atoms of Br is calculated as follows;

6.023 x 10²³ atoms = 80 g of Br

8.42 x 10¹⁸ atoms Br = ?

= (8.42 x 10¹⁸  x 80 g)/(6.023 x 10²³)

= 1.12 x 10⁻³ g

The mass in grams of  25 atoms of W is calculated as follows;

6.023 x 10²³ atoms = 74 g of W

25 atoms W = ?

= (25  x 74 g)/(6.023 x 10²³)

= 3.1 x 10⁻²¹ g

The mass in grams of  1 atom of Au is calculated as follows;

6.023 x 10²³ atoms = 197 g of Au

1 atom of Au = ?

= (1  x 197 g)/(6.023 x 10²³)

= 3.27 x 10⁻²² g

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Answer:

1.135986935e+39

Answer:

[tex]\boxed {\boxed {\sf 4.60 \times 10^{23} \ atoms \ Mg}}[/tex]

Explanation:

We are asked to find how many atoms of magnesium are in 0.764 moles of magnesium.

We convert moles to atoms using Avogadro's Number or 6.022 × 10²³. This is the number of particles (atoms, molecules, formula units, etc.) in 1 mole of a substance. In this case, the particles are atoms of magnesium. So, there are 6.022 × 10²³ atoms of magnesium in 1 mole of magnesium.

Convert using dimensional analysis and set up a conversion factor using Avogadro's Number.

[tex]\frac{6.022 \times 10^{23} \ atoms \ Mg}{1 \ mol \ Mg}[/tex]

We are converting 0.764 moles of magnesium to atoms, so we multiply by this value.

[tex]0.764 \ mol \ Mg *\frac{6.022 \times 10^{23} \ atoms \ Mg}{1 \ mol \ Mg}[/tex]

The units of moles of magnesium cancel.

[tex]0.764 *\frac{6.022 \times 10^{23} \ atoms \ Mg}{1 }[/tex]

[tex]0.764 *6.022 \times 10^{23} \ atoms \ Mg[/tex]

[tex]4.600808 \times 10^{23} \ atoms \ Mg[/tex]

The original value of moles (0.764) has 3 significant figures, so our answer must have the same. For the number we calculated, that is the hundredth place. The 0 in the thousandth place tells us to leave the 0 in the hundredth place.

[tex]4.60 \times 10^{23} \ atoms \ Mg[/tex]

0.764 moles of magnesium contains approximately 4.60 × 10²³ atoms of magnesium.

Answer:

Explanation:

i would say not d im not fully sure but id say c

When molecules present in a bowl of hot soup then they do vibration due to high kinetic energy.

Molecules are the example of chain substance, which can be prepared by the addition of two or more than 2 atoms of same or different nature.

In a hot soup bowl, kinetic energy of the molecules present in that soup increases due to which they move with higher velocity and also shows vibration in their mean position.

Hence, option (C) is correct i.e. vibrate.

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Answer:

b) theory

Explanation:

Answer:

theory or, conclusion is the answer

The equilibrium constant shows the extent of dissolution of a substance in solution. The molar solubility of the compound here is 1.2 * 10^-8 M.

The solubility product is the equilibrium constant that shows the extent to which a substnace is dissolved in soution.

Now let us set up the ICE table as shown;

               Cr(OH)3 (s) <-> Cr^3+ (aq) + 3OH^- (aq)

I                                           0                 0

C                                          +x               +3x

E                                          x                   3x

Ksp = [Cr^3+] [OH^- ]^3

6.3x10^-31 = [x] [3x]^3

6.3x10^-31 = 27x^4

x = 4√6.3x10^-31 /27

x = 1.2 * 10^-8 M

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#5

At 22min the temperature is at 40°C

#6

Graph ended at 20°C so condetion occured at 20°C

#7

After 70°C the matter got melted do its at liquid state

The reaction between copper II chloride and sodium sulfide as well as lead II nitrate and potassium sulfate both produce precipitates.

The solubility of a substance in water is in accordance with the solubility rules.  It is possible that a solid product may be formed when two aqueous solutions are mixed together. That solid product is referred to as a precipitate.

Now, we will consider each reaction individually to decode whether or not a precipitate is possible.

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Answer:

2,959.36

Explanation:

There are 2959.36 milligrams present in 2.89 x [tex]10^{24}[/tex]  CO2 molecules.

The smallest component of a substance which possesses both its chemical as well as physical characteristics. One or even more atoms make up molecules.

Such a measure of mass as well as weight that weighs 0.0154 grains or one-thousandth of a gram.

Calculation of milligram in CO2 molecule.

Mass = No. of molecule / molar mass.

Molar mass = 44.02 g/mol.

Mass = 2.89 x [tex]10^{24}[/tex]  /[tex]6.023 * 10^{23}[/tex]× 44.02 g/mol.

Mass = 2959.36 milligrams

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Answer:

Carbon Dioxide is and example of an element and Carbon is an example of compound

Answer: Định luật Raoult là một định luật hóa học vật lý, với ý nghĩa trong nhiệt động lực học. Được thành lập bởi nhà hóa học người Pháp François-Marie Raoult vào năm 1887, nó nói rằng áp suất một phần của mỗi thành phần của một hỗn hợp chất lỏng lý tưởng bằng với áp suất hơi của thành phần tinh khiết nhân với phần nốt ruồi của nó trong hỗn hợp. Kết quả là, việc giảm áp suất hơi tương đối của dung dịch pha loãng của chất tan không lây bằng với phần nốt ruồi của chất tan trong dung dịch.

Explanation: hope this helps :)

Answer:

Drawing conclusions

Explanation: