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ch4aika [34]
3 years ago
8

Chemistry help

Chemistry
1 answer:
Agata [3.3K]3 years ago
3 0

<em>Question 3. </em>

Answer:

They are equal in magnitude but opposite in sign.

Explanation:

Fusion is another word for <em>melting</em> and crystallization is another word for freezing.

They are opposite processes, so the heat you must add (positive sign) to melt a substance is equal to the heat released but with a negative sign.

ΔH(fus) = -ΔH(cryst)

===============

<em>Question 4. </em>

Answer:

18 400 J

Explanation:

There are two heat transfers in this question.

Total heat = heat to cool water + heat to freeze water

      q         =               q₁              +                q₂

      q         =            mCΔT          +        mΔH(freeze)

<em>Calculate q₁ </em>

m = 40.0 g

C = 4.184 J·K⁻¹g⁻¹

ΔT = T_f – T_i = 0 °C - 30 °C = -30 °C

q₁ = 40.0 × 4.184× (-30)

q₁ = <em>-5020 J </em>

<em>Calculate q₂ </em>

ΔH(cryst) = -334 J·g⁻¹

q₂ = 40.0 × (-334)

q₂ = <em>-13 360 J </em>

<em>Calculate the total heat </em>

q = -5 020 – 13 360

q = - 18 400 J

The negative sign shows that heat is removed, so you must remove

18 400 J.

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Compare which element would have larger first ionization energy: an alkali metal in Period 2 or an alkali metal in Period 4?
maria [59]

Answer:

An alkali metal present in period 2 have larger first ionization energy.

Explanation:

Ionization energy:

The amount of energy required to remove the electron from the atom is called ionization energy.

Trend along period:

As we move from left to right across the periodic table the number of valance electrons in an atom increase. The atomic size tend to decrease in same period of periodic table because the electrons are added with in the same shell. When the electron are added, at the same time protons are also added in the nucleus. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus. As a result of this greater nuclear attraction atomic radius decreases and ionization energy increases because it is very difficult to remove the electron from atom and more energy is required.

Trend along group:

As we move down the group atomic radii increased with increase of atomic number. The addition of electron in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased.

As the size of atom increases the ionization energy from top to bottom also  decreases because it becomes easier to remove the electron because of less nuclear attraction and as more electrons are added the outer electrons becomes more shielded and away from nucleus.  Thus alkali metal present in period 2 have larger ionization energy because of more nuclear attraction as compared to the alkali metal present in period 4.

6 0
3 years ago
Cierta cantidad de hidrogeno esta encerrada en una camara de platino a volumen constante. Cuando la camara se sumerge en un baño
salantis [7]

Answer:

-245.7°C es la temperatura del gas bajo 100 torr

Explanation:

Para resolver esta pregunta debemos hacer uso de la ley de Boyle que establece que la presión de un gas es directamente proporcional a la temperatura de este cuando el volumen permanece constante. La ecuación es:

P1T2 = P2T1

<em>Donde P es presión y T temperatura absoluta del estado inicial, 1, y final, 2.</em>

<em />

Reemplazando:

P1 = 1000torr

T2 = ? -Incógnita-

P2 = 100torr

T1 = 273K -Temperatura del hielo fundido = 0°C = 273K

1000torrT2 = 100torr273

T2 = 27.3K

27.3K - 273 =

<h3>-245.7°C es la temperatura del gas bajo 100 torr</h3>

<em />

3 0
3 years ago
How many grams of Mg are needed to produce 224 g of MgO in the complete reaction of Mg
zmey [24]

Answer:

134.4 g of Mg

Explanation:

reaction:

2Mg + O2 ➡️ 2MgO

1) find the mol of MgO

mol = mass / molar mass

mass = 224 g

molar mass = 24+16 = 40

mol = 224 / 40

= 5.6 moles

2 mol = 5.6 moles

2) find the mass of Mg

mass = mol × molar mass

mol = 5.6

molar mass = 24

mass = 5.6 × 24

= 134.4 g

7 0
3 years ago
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DedPeter [7]

Answer:

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Explanation:

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How can cool red giant be more luminous than a warmer main sequence star?
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Answer: C

Explanation:

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