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sergij07 [2.7K]
3 years ago
9

A scientist measures the standard enthalpy change for the following reaction to be 67.9 kJ:

Chemistry
1 answer:
hodyreva [135]3 years ago
6 0

Answer:

-252.5 kJ/mol = ΔH H2O(g)

Explanation:

ΔH Fe2O3 = -825.5kJ/mol

ΔH H2 = 0kJ/mol

ΔH Fe = 0kJ/mol

Based on Hess's law, ΔH of a reaction is the sum of ΔH of products - ΔH of reactants. For the reaction:

Fe2O3(s) + 3 H2(g) →2Fe(s) + 3 H2O(g)

ΔHr = 67.9kJ/mol = 3*ΔH H2O + 2*ΔHFe - (ΔH Fe2O3 + 3*Δ H2)

67.9kJ/mol = 3*ΔH H2O + 2*0kJ/mol - (ΔH -825.5kJ/mol + 3*Δ H2)

67.9 = 3*ΔH H2O(g) + 825.5kJ/mol

-757.6kJ/mol = 3*ΔH H2O(g)

<h3>-252.5 kJ/mol = ΔH H2O(g)</h3>
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Usually in this context you would be referring to the boiling and freezing point of a NaCl <em>solution</em> (saltwater) compared to pure H_{2}O. Sematics would be different for NaCl compound itself, you would say melting and boiling point for a solid substance- and the temperatures would be very, very radical (high). 
The boiling point of pure water is 100 degrees C (212 F), and the freezing/melting point is below 0 degrees C (32 F). For a salt water solution, the boiling point is raised and the melting point is lowered. This means that water will stay liquid for an increased range of temperature. Depending on the amount of NaCl solute in the water, the boiling and melting points may change a few degrees.
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3 years ago
Write a question you have about Titan or about methane that could help you determine what happened to the lake
Sergeeva-Olga [200]

Answer: what would swimming in mathane lake on titan feel like.

Explanation:

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3 years ago
Which chemical equation shows that the total mass during a chemical reaction stays the same?
k0ka [10]

Answer:

  • Option A) <u><em>Mg + Cl₂ → MgCl₂</em></u>

Explanation:

The law of conservation of mass is guaranteed in a chemical equation. Since the mass of the atoms do not change, that means that the number of each kind of atoms in the reactant side is equal to the number of atoms of the same kind in the product side.

The first equation is:

<em><u>A) Mg + Cl₂ → MgCl₂</u></em>

<u />

Number of atoms:

        atom      Reactant side        Product side

          Mg                1                              1

           Cl                 2                             2

Therefore, the table displays that there are the same number of atoms of each kind on both sides, showing that<em> the total mass during the chemical reaction stays the same.</em>

<u />

<em><u>B) NaOH + MgCl₂ → NaCl + MgOH</u></em>

This equation displays 2 atoms of Cl on the left side and 1 atom of Cl on the right side; thus, it is not showing that the total mass stays the same during the chemical reaction.

<em />

<u><em>C) 2Na + 2H₂O → NaOH + H₂</em></u>

Neither the sodium, nor oxygen, nor hydrogen atoms are balanced. Thus, this does not show that the total mass stays the same.

<u><em /></u>

<u><em>D) H₂O + O₂ → H₂O</em></u>

The reactant side contains 3 oxygen atoms and the product side contains 1 atoms of oxygen; thus, this is not balanced: it does not show that the total mass stays de same during the chemical reaction.

5 0
3 years ago
Read 2 more answers
What is the thermal energy needed to vaporize 18.02g of water at 100°C? The Heat of Vaporization for water is 40.650 kJ/mol.
podryga [215]

Answer:

40.7 kJ

Explanation:

Applying,

q = c'n.................. Equation 1

Where q = Thermal Heat, c' = Heat of vaporization of water, n = number of mole of water.

But,

n = mass(m)/Molar mass(m')

n = m/m'............... Equation 2

Substitute equation 2 into equation 1

q = c'(m/m')............. Equation 3

Given: c' = 40.650 KJ/mol, m = 18.02 g

Constant: m' = 18 g/mol

Substitute into equation 3

q = 40.650(18.02/18)

q = 40.695 kJ

q ≈ 40.7 kJ

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3 years ago
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I think the answer is A
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