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mart [117]
3 years ago
13

Which of the following best defines the internal energy of a system?

Chemistry
1 answer:
Anarel [89]3 years ago
7 0
 <span>In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of atoms within molecules or crystals. It includes the energy in all the chemical bonds, and the energy of the free, conduction electrons in metals.</span>
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Given the following at 25C calculate delta Hf for HCN (g) at 25C. 2NH3 (g) +3O2 (g) + 2CH4 (g) ---&gt; 2HCN (g) + 6H2O (g) delta
AysviL [449]

<u>Answer:</u> The \Delta H_f for HCN (g) in the reaction is 135.1 kJ/mol.

<u>Explanation:</u>

Enthalpy change is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. The equation used to calculate enthalpy change is of a reaction is:

\Delta H_{rxn}=\sum [n\times \Delta H_f(product)]-\sum [n\times \Delta H_f(reactant)]

For the given chemical reaction:

2NH_3(g)+3O_2(g)+2CH_4(g)\rightarrow 2HCN(g)+6H_2O(g)

The equation for the enthalpy change of the above reaction is:

\Delta H_{rxn}=[(2\times \Delta H_f_{(HCN)})+(6\times \Delta H_f_{(H_2O)})]-[(2\times \Delta H_f_{(NH_3)})+(3\times \Delta H_f_{(O_2)})+(2\times \Delta H_f_{(CH_4)})]

We are given:

\Delta H_f_{(H_2O)}=-241.8kJ/mol\\\Delta H_f_{(NH_3)}=-80.3kJ/mol\\\Delta H_f_{(CH_4)}=-74.6kJ/mol\\\Delta H_f_{(O_2)}=0kJ/mol\\\Delta H_{rxn}=-870.8kJ

Putting values in above equation, we get:

-870.8=[(2\times \Delta H_f_{(HCN)})+(6\times (-241.8))]-[(2\times (-80.3))+(3\times (0))+(2\times (-74.6))]\\\\\Delta H_f_{(HCN)}=135.1kJ

Hence, the \Delta H_f for HCN (g) in the reaction is 135.1 kJ/mol.

8 0
3 years ago
Differentiate between the three types of simple permanent tissues on the basis of their cell walls​
True [87]

Answer:

Parenchyma is the most simple and specialized tissue which is concerned mainly with the vegetative activities of the plant. The cells are isodiametric with well-developed intercellular spaces, vacuolated cytoplasm and cellulosic cell wall.

Collenchyma is the tissue of the primary body. The cells of the tissue contain protoplasm and are living without intercellular spaces. The cell wall articulate at the corners and are made up of cellulose, hemicellulose, and pectin.

Sclerenchyma is the thick-walled cell tissue. In the beginning, the cell is living and have protoplasm, but due to deposition of impermeable secondary board lignin, they become dead thick and hard.

5 0
3 years ago
Which of the following best describes an empirical formula?
Monica [59]

Answer:

Option C :

a chemical formula that shows the relative number of each type of atom in a molecule, using the smallest possible ratio

Explanation:

Empirical Formula:

Empirical formula is the simplest ration of atoms in the molecule but not all numbers of atoms in a compound.

So,

Tha ration of the molecular formula should be divided by whole number to get the simplest ratio of molecule

For Example

      C₂H₆O₂ Consist of  Carbon (C), Hydrogen (H), and Oxygen (O)

Now

Look at the ratio of these three atoms in the compound

                         C : H : O

                         2 : 6 : 2

Divide the ratio by two to get simplest ratio

                          C : H : O

                         2/2 : 6/2 : 2/2

                             1 : 3 : 1

So for the empirical formula the simplest ratio of carbon to hydrogen to oxygen is 1:3:1

So the empirical formula will be

                     Empirical formula of C₂H₆O₂ = CH₃O

So, Option C is correct :

a chemical formula that shows the relative number of each type of atom in a molecule, using the smallest possible ratio

6 0
3 years ago
Which of the following are examples of chemical changes? Select all that apply.
Natali5045456 [20]

Answer:

b. milk spoiling and c. firecrackers exploding

Explanation:

These are both chemical changes, the composition of them change when this happens and it cannot be reversed

6 0
2 years ago
The name 3-chloro-2-propylbutane is not an accepted name for the compound described. what would be the correct name for this com
Illusion [34]
The longest hydrocarbon chain in the given compound is hexane, therefore it is the parent chain to be considered with one methyl group attached to the 3rd carbon and one chloro attached on the 2nd carbon, therefore the name of the compound is 2-chloro-3-methylhexane
3 0
3 years ago
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