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Sonbull [250]
3 years ago
6

1) Which of the following is an example of an endothermic process?

Chemistry
2 answers:
svp [43]3 years ago
6 0

<u>Answer:</u>

<u>For 1:</u> The correct answer is Option a.

<u>For 2:</u> The correct answer is (-2222) - [(-1182) + (-1144)] kJ

<u>Explanation:</u>

  • <u>For 1:</u>

Endothermic reactions are defined as the reactions in which energy is absorbed by the system.

Exothermic reactions are defined as the reactions in which heat is released by the system.

For the given options:

<u>Option a:</u> In this case, solid chocolate bar is meting with increase in temperature. Thus, it is absorbing heat from the surrounding and is considered as an endothermic reaction.

<u>Option b:</u> In this case, fruit are freezing in the freezer. Thus, it is releasing heat to the surrounding and is considered as an exothermic reaction.

<u>Option c:</u> Combustion reactions are defined as the reactions in which hydrocarbon reacts with oxygen gas to release carbon dioxide and water molecule with the release of heat. Thus, it considered as an exothermic reaction.

<u>Option d:</u> In this case, water molecules present in the air are getting condensed. Thus, it is releasing heat to the surrounding and is considered as an exothermic reaction.

From the above information, the correct answer is option a.

  • <u>For 2:</u>

According to Hess’s law, the heat absorbed or evolved in chemical equation is same whether the process is occuring in one step or in several steps.

According to this law, the chemical equation is treated as the ordinary algebraic expression which can be added or subtracted to get the required equation. This means the enthalpy change of the overall reaction will be equal to the sum of the enthalpy changes of the intermediate reactions.

We are given 3 intermediate balanced reactions:

Equation 1:  3C+3O_2\rightarrow 3CO_2;\Delta H_1=-1182kJ

Equation 2:  4H_2+2O_2\rightarrow 4H_2O;\Delta H_2=-1144kJ

Equation 3:  C_3H_8+5O_2\rightarrow 3CO_2+4H_2O;\Delta H_3=-2222kJ

Final Equation:  C_3H_8\rightarrow 3C+4H_2

By adding Equation 3 and reverse reaction of Equation 1 and Equation 2, we will get the enthalpy of final equation.

\Delta H_{final}=\Delta H_{3}-[\Delta H_1+\Delta H_2]\\\\\Delta H_{final}=-2222+[(-1182)+(-1144)]kJ

Hence, the correct answer is (-2222) - [(-1182) + (-1144)] kJ

Aleks04 [339]3 years ago
3 0
For the first question, the correct answer among the choices listed is option A, a chocolate bar melting in hot car. It is an endothermic process because it absorbs heat energy for it to be melted. For the second question, it think the correct answer is the last option, <span>(-2222) + (-1182) - (-1144).</span>
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Lemur [1.5K]

Answer:

Concentration of Flourine = 24.756%

Explanation:

Given that :

High-density polyethylene may be flourinated by inducing the random substitution of Flourine atoms for hydrogen.

the objective is to determine he concentration of Flourine (in wt%) that must be added if this substitution occurs for 12% of all the original hydrogen atoms.

At standard conditions , the atomic weight of the these compounds are as follows:

Carbon = 12.01 g/mol

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Fluorine = 19.00 g/mol

Hydrogen = 1.008 g/mol

Oxygen = 16.00 g/mol

The chemical formula for polyethylene = (CH₂ - CH₂)ₙ

Therefore, for two carbons, there will be 4 hydrogens;

i.e

(CH₂ - CH₂)₂

( C₂H₄ - C₂H₄ )

Suppose the number of original hydrogen = 4moles

number of moles of Flourine F = 12% of 4

= 0.12 × 4

= 0.48 mol

∴ the number of remaining moles of Hydrogen is:

= 4 - 0.48

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number of moles of Carbon = 2 moles

∴ the mass of flourine F = number of moles of F × molar mass of F

= 0.48 × 19

= 9.12

The total mass of the compound now is = (0.48 × 19 ) + (3.52 × 1) + (2× 12)

= 9.12 + 3.52 + 24

= 36.64

Concentration of Flourine = (mass of flourine/total mass) × 100

Concentration of Flourine = (9.12/36.84 ) × 100

Concentration of Flourine = 0.24756 × 100

Concentration of Flourine = 24.756%

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3 years ago
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The correct answer is option D, that is, the ions are now combining to reduce their concentrations.

Explanation:

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PbCl₂ (s) ⇒ Pb²⁺ (aq) + 2Cl⁻ (aq)

It is mentioned that the value of Ksp is 1.8 × 10⁻²

As the solubility product is very less or negligible for this reaction that signifies that the ions produced are getting combined, resulting in the reduction of the concentration of the ions and enhancing the formation of the solid lead chloride. Therefore, they associate together to produce solid lead chloride.  

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OverLord2011 [107]
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How many moles of KOH are required to produce 4.79 g K3PO4 according to the following reaction? 3KOH + H3PO4 -----&gt; K3PO4 + 3
8_murik_8 [283]

Answer:

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From the equation, the mole ratio of KOH : K3PO4 = 3 :1,

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So, using this ratio, let the no. of moles of KOH required to be y.

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If you don't find exactly 0.677 moles as one of the options, go for the closest one. A very slight error may occur because of taking different significant figures of atomic masses when calculating.

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Answer:

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Explanation:

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In supplementation, the eruptions also discharge bits of rocks like pyroxene, potolivine, amphibole, feldspar that are in turn enriched with magnesium, iron, and potassium. As an outcome, the areas which comprise huge deposits of the volcanic soil are quite fertile.  

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