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Deffense [45]
3 years ago
5

Chalk markings cannot be easily rubbed off from a black board if kept for a long time.why?

Chemistry
1 answer:
snow_tiger [21]3 years ago
3 0

The chalk particles embed themselves into the small pores on the surface.

Although a chalkboard seems smooth to the touch, it is quite rough at the microscopic level, with <em>pores</em> that reach below the surface.

When you drag chalk across the board, friction causes small particles of chalk to rub off onto the surface.

If you leave the markings for a long time, some of the chalk particles will work their way into the pores.

A brush will remove the surface particles, but <em>it will not be able to get at the particles in the pores</em>.

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During the process of sublimation,
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During this process. A. Solid turns directly into a Gas.
5 0
3 years ago
Where does the chemical energy to produce ATP come from
aleksandrvk [35]

Answer:

glucose

Explanation:

Chemical energy is stored in the bonds that hold the molecule together. ADP can be recycled into ATP when more energy becomes available. The energy to make ATP comes from glucose. Cells convert glucose to ATP in a process called cellular respiration.

7 0
2 years ago
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Determine the missing species:
Galina-37 [17]

Answer: 4. ^{0}_{-1}\textrm{e} and ^{0}_{1}\textrm{e}

Explanation:

a) The given reaction is ^{41}_{20}\textrm{Ca}+^{x}_{y}\textrm{X}\rightarrow ^{41}_{19}\textrm {K}

As the mass on both reactant and product side must be equal:

41+x=41

x=0

As the atomic number on both reactant and product side must be equal:

20+y=19

y=-1

^{41}_{20}\textrm{Ca}+^{0}_{-1}\textrm{e}\rightarrow ^{41}_{19}\textrm {K}

b) ^{15}_{8}\textrm{O}\rightarrow ^{15}_{7}\textrm{N}+^{x}_{y}\textrm{X}

Total mass on reactant side = total mass on product side

15 =15 + x

x = 0

Total atomic number on reactant side = total atomic number on product side

8 = 7 + y

y = 1

^{15}_{8}\textrm{O}\rightarrow ^{15}_{7}\textrm{N}+^{0}_{1}\textrm{e}

5 0
2 years ago
Given the formula representing a compound: what is a chemical name of this compound? 2-pentene 2-pentyne 3-pentene 3-pentyne
Aleks [24]
The question is incomplete. Complete question is attached below.
..........................................................................................................................

Correct Answer: <em>Option 1) 2-pentene</em>

Reason:
Following are the IUPAC rules for naming the compound
1) Select the longest carbon chain. In present case longest carbon chain has 5 carbon atom. Hence, it is a pentane derivative.
2) In case of alkene, replace 'e' of alkane by 'ene'
3) Give lowest number to function group. In present case, it is double bond.

Applying above rules, the IUPAC name of compound is 2-pentene

4 0
3 years ago
In terms of energy, how would you classify the following chemical reaction?
olga_2 [115]

1. Answer;

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Explanation;

-Exothermic reactions are types of chemical reactions in which heat energy is released to the surroundings. Since enthalpy change is the difference between the energy of products an that of reactants. It means that in an exothermic reaction the energy of products is less than that of products. In this case an energy of 315kJ is released to the surroundings.

2. Answer;

Conserved

-The total amount of energy before and after a chemical reaction is the same. Thus, energy is conserved.

Explanation;

-According to the law of conservation of energy, energy is neither created nor destroyed. Energy may change form during a chemical reaction. For example, energy may change form from chemical energy to heat energy when gas burns in a furnace. However, the exact amount of energy remains after the reaction as before, which is true for all chemical reactions.

3 0
3 years ago
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