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3 years ago

Chất có ở đâu ? nước tự nhiên là chất hay hỗn hợp

Chemistry

1 answer:

Lynna [10]3 years ago

4 0

Answer:

Water, H2O, is a pure substance, a compound made of hydrogen and oxygen. Although water is the most abundant substance on earth, it is rarely found naturally in its pure form. Most of the time, pure water has to be created. Pure water is called distilled water or deionized water.

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Pls help and i will mark brainliest

myrzilka [38]

Answer:

No. 3 lithium

Explain that lithium has 3 protons and 3 electrons. There are 2 electrons on the first energy level and 1 electron on the second

No. 4 Hydrogen (H) and helium (He) have a valence shell containing one and two electrons respectively. They make up the first period (row) of the periodic table. Their valence electron/s are in the first energy level (n=1) , as is denoted by 1s1 and 1s2 .

That's all i dont know if this is right though. 

6 0

2 years ago

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What is the energy of a 933 nm wave?

vovikov84 [41]

E=hc/l

E=(6.626 x 10-34 J s)(3.0 x 108m/s )=2.88 x 10-19J6.90 x 10-7m

8 0

2 years ago

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A measure of the kinetic energy of particle motion within a substance is temperature.

Natali5045456 [20]

I believe it’s true when particles move they create heat

4 0

3 years ago

Read 2 more answers

What is the molarity of 225 grams of Cu(NO2)2 in a total volume of 2.59 L?

Kay [80]

Answer:

The molarity is 0.56 $\frac{moles}{L}$

Explanation:

In a mixture, the chemical present in the greatest amount is called a solvent, while the other components are called solutes. Then, the molarity or molar concentration is the number of moles of solute per liter of solution.

In other words, molarity is the number of moles of solute that are dissolved in a given volume.

The Molarity of a solution is determined by:

$Molarity (M)=\frac{number of moles of solute}{Volume}$

Molarity is expressed in units ( $\frac{moles}{liter}$ ).

Then you must know the number of moles of Cu(NO₂)₂. For that it is necessary to know the molar mass. Being:

Cu: 63.54 g/mol
N: 14 g/mol
O: 16 g/mol

the molar mass of Cu(NO₂)₂ is:

Cu(NO₂)₂= 63.54 g/mol + 2*(14 g/mol + 2* 16 g/mol)= 155.54 g/mol

Now the following rule of three applies: if 155.54 g are in 1 mole of the compound, 225 g in how many moles are they?

$moles=\frac{225 g*1 mole}{155.54 g}$

moles= 1.45

So you know:

number of moles of solute= 1.45 moles
volume=2.59 L

Replacing in the definition of molarity:

$Molarity=\frac{1.45 moles}{2.59 L}$

Molarity= 0.56 $\frac{moles}{L}$

The molarity is 0.56 $\frac{moles}{L}$

5 0

3 years ago

Describe how particles of iron (Fe) an oxygen (O2) react to how produce oxide (Fe2O3), also known as rust.

forsale [732]

Answer:

Described by a redox reaction below

Explanation:

Iron(III) oxide is an ionic compound, since it consists of a metal, iron, and a nonmetal, oxygen.

Ionic compounds are formed when metals lose their valence electrons in order to have an octet in their previous shell and donate them to nonmetal atoms, so that nonmetals fill their outer shell to have an octet.

As a result, positive ions (cations) and negative ions (anions) are formed. When iron reacts with oxygen, the following reaction takes place:

$4 Fe (s) + 3 O_2 (g)\rightarrow 2 Fe_2O_3 (s)$

This is a redox (oxidation–reduction) reaction, since we have electron loss and gain. Four iron atoms lose a total of 12 electrons to obtain a +3 charge in the final compound, while 3 oxygen molecules gain these 12 electrons to become 6 oxide anions with a -2 charge.

4 0

3 years ago