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2 years ago

Which material has a crystalline structure at room temperature ( 20 degrees Celsius )

Chemistry

2 answers:

Sauron [17]2 years ago

8 0

It's 2, glass. Water, nitrogen, and sucrose don;t have a crystalline structure.

Musya8 [376]2 years ago

8 0

Answer:

Sucrose. Option 4 is correct.

Explanation:

Crystallinity can be defined as the degree of structural order in a solid.

Let us take a look at each of the material mentioned in the question..

The first one is WATER. Water has the molecular formula of H2O, it is bent at an angle approximately 104.5 degrees. Because of its molecular form as liquid, WATER is amorphous and NOT crystalline.

The second material is GLASS: GLASS do not crystallized when they become hardened.

The third material is Nitrogen, NITROGEN is a non metallic element of group 15. Although solid nitrogen have crystalline modifications, they still exist as amorphous.

The fourth material is sucrose. SUCROSE is a disaccharide. It is a crystalline white solid.

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Be sure to answer all parts. ΔH o f of hydrogen chloride [HCl(g)] is −92.3 kJ/mol. Given the following data, determine the ident

Akimi4 [234]

Answer:

NH₄Cl(s) → NH₃(g) + HCl(g)

ΔH°rxn 74,89 kJ/mol

Explanation:

The change in enthalpy of formation (ΔHf) is defined as the change in enthalpy in the formation of a substance from its constituent elements. For HCl(g):

<em>(1) </em>¹/₂H₂(g) + ¹/₂ Cl₂ → HCl(g) ΔH = -92,3 kJ/mol

It is possible to sum ΔH of different reactions to obtain ΔH of a global reaction (Hess's law).

For the reactions:

<em>(2) </em>N₂(g) + 4H₂(g) + Cl₂(g) → 2NH₄Cl(s) ΔH°rxn = −630.78 kJ/mol

<em>(3)</em> N₂(g) + 3H₂(g) → 2NH₃(g) ΔH°rxn = −296.4 kJ/mol

The sum of -(2) + (3) gives:

<em>-(2) </em>2NH₄Cl(s) → N₂(g) + 4H₂(g) + Cl₂(g) ΔH°rxn = +630.78 kJ/mol

<em>(3)</em> N₂(g) + 3H₂(g) → 2NH₃(g) ΔH°rxn = −296.4 kJ/mol

<em>-(2) + (3) </em>2NH₄Cl(s) → 2NH₃(g) + H₂(g) + Cl₂(g)

ΔH°rxn = +630.78 kJ/mol −296.4 kJ/mol = +334,38 kJ/mol

Now, the sum of -(2) + (3) + 2×(1)

<em>-(2) + (3) </em>2NH₄Cl(s) → 2NH₃(g) + H₂(g) + Cl₂(g) ΔH°rxn = +334,38 kJ/mol

<em>2×(1) </em>H₂(g) + Cl₂(g)→ 2HCl(g) ΔH = 2×-92,3 kJ/mol

<em>-(2) + (3) + 2×(1) </em>2NH₄Cl(s) → 2NH₃(g) + 2HCl(g)

ΔH°rxn = +334,38 kJ/mol + 2×-92,3 kJ/mol = 149,78 kJ/mol

The reaction of:

<em>NH₄Cl(s) → NH₃(g) + HCl(g)</em>

<em>Has ΔH°rxn = 149,78kJ/mol / 2 = 74,89 kJ/mol</em>

I hope it helps!

8 0

1 year ago

Based on the results of this lab, write a short paragraph that summarizes how to distinguish physical changes from chemical chan

Kaylis [27]

Physical changes occur when the properties of a substance are retained and/or the materials can be recovered after the change. Chemical changes involve the formation of a new substance. Formation of a gas, solid, light, or heat are possible evidence of chemical change.

6 0

1 year ago

Read 2 more answers

Which element has six valence electrons in each of its atoms in the ground state?

baherus [9]

Answer is: selenium (Se).
1) electron configuration: ₃₄Se 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4sp⁴.
2) ₃₃As 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4sp³.
3) ₃₆Kr 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4sp⁶.
4) ₃₁Ga 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4sp¹.
Valence electrons of selenium are 4s²4sp⁴.

7 0

2 years ago

Read 2 more answers

Calculate the hydrogen ion concentration in a solution of fruit juice having a pH of 4.25.

Airida [17]

Answer:

<h3>The answer is option B</h3>

Explanation:

The pH of a solution can be found by using the formula

pH = - log [ H+ ]

To find the hydrogen ion concentration substitute the pH into the above formula and solve for the [ H+ ]

From the question