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Dvinal [7]
4 years ago
8

Which of the following does not describe elements?

Chemistry
2 answers:
postnew [5]4 years ago
6 0
The statement that does not describe elements would be that they can be separated by a chemical reaction. This is not the case, an element is a pure substance that can't be degraded into any other constituent that would form it. They are building blocks composed by atoms.
shusha [124]4 years ago
3 0

Answer: Option (b) is the correct answer.

Explanation:

Elements are defined as the substance which contain same type of atoms.

An element cannot be divided into simpler substances by any physical or chemical means.

For example, a piece of aluminium will contain only atoms of aluminium.

The periodic table contains all the elements present in nature.

Thus, we can conclude that out of the given options the statement they can be separated by a chemical reaction, does not describe elements.

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Calculate ΔH∘f (in kilojoules per mole) for benzene, C6H6, from the following data: 2C6H6(l) + 15O2(g)→12CO2(g)+6H2O(l) ΔH∘=−653
Pachacha [2.7K]

Answer: 48.6 kJ/mol

Explanation:

The balanced chemical reaction is,

2C_6H_6(l)+15O_2(g)\rightarrow 12CO_2(g)+6H_2O(l)

The expression for enthalpy change is,

\Delta H=\sum [n\times \Delta H_f(product)]-\sum [n\times \Delta H_f(reactant)]

\Delta H=[(n_{CO_2}\times \Delta H_{CO_2})+(n_{H_2O}\times \Delta H_{H_2O})]-[(n_{O_2}\times \Delta H_{O_2})+(n_{C_6H_6}\times \Delta H_{C_6H_6})]

where,

n = number of moles

\Delta H_{O_2}=0 (as heat of formation of substances in their standard state is zero

Now put all the given values in this expression, we get

-6534.0=[(12\times -393.5)+(6\times -285.8)]-[(15\times 0)+(2\times \Delta H_{C_6H_6})]

\Delta H_{C_6H_6}=48.6kJ/mol

Therefore, the enthalpy change for benzene is 48.6 kJ/mol

4 0
3 years ago
Help me with this please!
Annette [7]

The correct answer is 9.7 grams because mg are 1,000 difference to grams.

8 0
4 years ago
Changing from liquid to gas is a chemical change.<br> True<br> False
Korolek [52]

Answer:

This is False

Explanation:

A chemical change is when the matter is completely changed.

When you have water and boil it to be a gas, it is still the same matter, just in a different form.

I hope this helps :)

6 0
3 years ago
Read 2 more answers
An atom has three full orbitals in its second energy level. How many electrons are present in the second energy level of the ato
zloy xaker [14]

What elem eat is this? That has three orbitals? Usually the first orbital will contain only two electrons. The second orbital would contain four, the third would contain 16

8 0
3 years ago
The rate constant for this first‑order reaction is
jenyasd209 [6]

Answer:

t = 5.7634 s

Explanation:

  • A → Pdts
  • - rA = K (CA)∧α = - δCA/δt

∴ T = 400°C

∴ α = 1 ....first-order

∴ CAo = 0.950 M

∴ CA = 0.300 M

⇒ t = ?

⇒ - δCA/δt = K*CA

⇒ - ∫δCA/CA = K*∫δt

⇒ Ln (CAo/CA) = K*t

⇒ t = Ln(CAo/CA) / K

⇒ t = (Ln(0.950/0.300)) / (0.200 s-1)

⇒ t = 1.1527 / 0.200 s-1

⇒ t = 5.7634 s

5 0
3 years ago
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