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3 years ago

When a solid melts, why does it absorb energy?

1 answer:

5 0

In order for the molecules to actually separate from each other, more energy must be added. This energy, called heat of fusion or heat of melting, is absorbed by the particles as potential energy as the solid changes to a liquid. I hope this helps

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Which of the following coefficients are needed to balance the combustion reaction of ethanol?

djyliett [7]

Answer is: d. 3,2,3.

Balanced chemical reaction: CH₃CH₂OH + 3O₂ → 2CO₂ + 3H₂O.
CH₃CH₂OH is ethanol.
O₂ is molecule of oxygen.
CO₂ is carbon(IV) oxide.
H₂O is water.
There are same number of atoms (oxygen, carbon and hydrogen) on both side of balanced chemical reaction:
2 atoms of carbon.
6 atoms of hydrogen.
7 atoms of oxygen.

5 0

3 years ago

A solution has a pH of 2.5. what is the H+

romanna [79]

<u>Answer: </u>The concentration of $H^+$ in the solution is $3.16\times 10^{-3}M$

<u>Explanation:</u>

pH is defined as the negative logarithm of hydrogen ion concentration present in the solution.

$pH=-\log [H^+]$ .....(1)

We are given:

pH of solution = 2.5

Putting values in equation 1, we get:

$2.5=-\log [H^+]$

$[H^+]=10^{-2.5}$

$[H^+]=3.16\times 10^{-3}M$

Hence, the concentration of $H^+$ in the solution is $3.16\times 10^{-3}M$

4 0

3 years ago

Calculate the pH at the equivalence point for the titration of 0.110 M methylamine (CH3NH2) with 0.110 M HCl. The Kb of methylam

nikklg [1K]

The reaction between the reactants would be:

CH₃NH₂ + HCl ↔ CH₃NH₃⁺ + Cl⁻

Let the conjugate acid undergo hydrolysis. Then, apply the ICE approach.

CH₃NH₃⁺ + H₂O → H₃O⁺ + CH₃NH₂
I 0.11 0 0
C -x +x +x
E 0.11 - x x x

Ka = [H₃O⁺][CH₃NH₂]/[CH₃NH₃⁺]

Since the given information is Kb, let's find Ka in terms of Kb.

Ka = Kw/Kb, where Kw = 10⁻¹⁴

So,
Ka = 10⁻¹⁴/5×10⁻⁴ = 2×10⁻¹¹ = [H₃O⁺][CH₃NH₂]/[CH₃NH₃⁺]
2×10⁻¹¹ = [x][x]/[0.11-x]
Solving for x,
x = 1.483×10⁻⁶ = [H₃O⁺]

Since pH = -log[H₃O⁺],
pH = -log(1.483×10⁻⁶)
<em>pH = 5.83</em>

4 0

4 years ago

When the first periodic table of the elements was published, the elements were arranged by atomic mass. Although several element

Inessa [10]

<h3><u>Answer;</u></h3>

New information changed the understanding of the atom’s structure.

<h3><u>Explanation;</u></h3>

<em><u>Mendeleev is know as the Father of the Modern Periodic Table. His table allowed scientists to predict the existence of elements that hadn't been discovered.</u></em>
Mendeleev saw that when the elements were arranged in order of increasing atomic mass, those that had similar properties occurred in a repeating pattern. He predicted that elements yet to be found would fill the gaps in his table.

3 0

4 years ago

Poliomyelitis is caused by a virus that spreads easily in human populations. Most people with polio infections show no symptoms

Sonja [21]

Answer:

a multipolar neuron that has two or more dendrites and a single axon

Explanation:

5 0

4 years ago