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Darina [25.2K]
2 years ago
12

Which represents an endothermic reaction

Chemistry
2 answers:
aalyn [17]2 years ago
7 0

Answer:

melting from ice cube to water

Explanation:

this is because the object gains heat and melting occurs in the object

Alex_Xolod [135]2 years ago
7 0

Answer:it is b

Explanation:

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What volume of 15.6M NH4OH is needed to make 500. mL of 3.00M solution?
Mariana [72]

Answer:

V₁  = 96.2 mL

Explanation:

Given data:

Initial volume of NH₄OH required = ?

Initial molarity = 15.6 M

Final molarity = 3.00 M

Final volume = 500.0 mL

Solution:

Formula:

M₁V₁  =  M₂V₂

M₁ = Initial molarity

V₁  =  Initial volume of NH₄OH

M₂ =Final molarity

V₂ = Final volume

Now we will put the values.

15.6 M ×V₁  =  3.00 M×500.0 mL

15.6  M ×V₁  = 1500 M.mL

V₁  = 1500 M.mL /15.6 M

V₁  = 96.2 mL

6 0
3 years ago
Correct answer. 9. The mass number of an element is the number of? ​
Elis [28]

Answer:

The mass number is defined as the total number of protons and neutrons in an atom. The number of neutrons = mass number − atomic number.

4 0
3 years ago
Arrange the following H atom electron transitions in order of decreasing wavelength of the photon absorbed or emitted:
Katyanochek1 [597]

The decreasing order of wavelengths of the photons emitted or absorbed by the H atom is : b → c → a → d

Rydberg's formula :

                                   \frac{1}{\lambda} = R_h (\frac{1}{n_1^2}-\frac{1}{n_2^2} ),

where  λ is the wavelength of the photon emitted or absorbed from an H atom electron transition from n_1 to n_2 and R_h = 109677 is the Rydberg Constant. Here n_1 and  n_2 represents the transitions.

(a) n_1 =2 to n_2 = infinity

            \frac{1}{\lambda} = 109677\times (\frac{1}{2^2}-\frac{1}{\infty^2}  ) = 109677/4     [since 1/infinity = 0] Therefore, \lambda = 4 / 109677 = 0.00003647 m

(b) n_1=4 to  n_2 = 20

           \frac{1}{\lambda} = 109677\times (\frac{1}{4^2}-\frac{1}{20^2}  ) = 6580.62

Therefore,  \lambda = 1 / 6580.62 = 0.000152 m

(c) n_1=3 to  n_2 = 10

          \frac{1}{\lambda} = 109677\times (\frac{1}{3^2}-\frac{1}{10^2}  ) = 11089.56

Therefore,  \lambda = 1 / 11089.56 = 0.00009 m

(d)  n_1=2 to  n_2 = 1

          \frac{1}{\lambda} = 109677\times (\frac{1}{2^2}-\frac{1}{1^2}  ) = - 82257.75

Therefore,  \lambda = 1 /82257.75  = - 0.0000121 m  

[Even though there is a negative sign, the magnitude is only considered because the sign denotes that energy is emitted.]

So the decreasing order of wavelength of the photon absorbed or emitted is b → c → a → d.

Learn more about the Rydberg's formula athttps://brainly.com/question/14649374

#SPJ4

8 0
1 year ago
The energy that a log has is transformed when burned. How does the chemical energy of the log compare to the heat and light ener
SCORPION-xisa [38]
The amount of chemical energy is equal to the amount of heat and light energy.

This is due to the principle of conservation of energy, which states that the total energy of a system remains constant. 
4 0
3 years ago
Which best explains why water is able to “stick” to the side of glass?
AveGali [126]

Explanation:

Adhesion means the ability to stick on the surface of another substance.

Water exhibits adhesive forces due to which it is able to stick to the glass.  Due to adhesive forces water spreads over the surface of glass and sticks to it.

These adhesive forces between the glass and water enough that it deforms the spherical shape of water molecules and help them stick to the surface of glass. As a result, adhesive forces overcome the repulsion between like molecules.

Hence, water is able to “stick” to the side of glass due to strong adhesive forces.


4 0
3 years ago
Read 2 more answers
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