Which statements accurately describe the rock cycle? Check all that apply.

Consider the reaction directly below and answer parts a and b. C6H4(OH)2 (l) + H2O2 (l) à C6H4O2 (l) + 2 H2O (l)

dedylja [7]

Answer:

a. -206,4kJ

b. Surroundings will gain heat.

c. -115kJ are given off.

Explanation:

It is possible to obtain ΔH of a reaction using Hess's law that consist in sum the different ΔH's of other reactions until obtain the reaction you need.

Using:

(1) C₆H₄(OH)₂(l) → C₆H₄O₂(l) + H₂(g) ΔH: +177.4 kJ

(2) H₂(g) + O₂(g) → H₂O₂ (l) ΔH: -187.8 kJ

(3) H₂(g) + 1/2O₂(g) → H₂O(l) ΔH: -285.8 kJ

It is possible to obtain:

C₆H₄(OH)₂(l) + H₂O₂(l) → C₆H₄O₂(l) + 2H₂O(l)

From (1)-(2)+2×(3). That is:

(1) C₆H₄(OH)₂(l) → C₆H₄O₂(l) + H₂(g) ΔH: +177.4 kJ

-(2) H₂O₂(l) → H₂(g) + O₂(g) ΔH: +187.8 kJ

2x(3) 2H₂(g) + O₂(g) → 2H₂O(l) ΔH: 2×-285.8 kJ

The ΔH you obtain is:

+177,4kJ + 187,8kJ - 2×285.8 kJ = -206,4kJ

b. When ΔH of a reaction is <0, the reaction is exothermic, that means that the reaction produce heat and the surroundings will gain this heat.

c. 20,0g of H₂O are:

20,0g× $\frac{1mol}{18,01g}$ = 1,11 mol H₂O

As 2 moles of H₂O are produced when -206,4kJ are given off, when 1,11mol of H₂O are produced, there are given off:

1,11mol H₂O× $\frac{-206,4kJ}{2mol}$ = -115kJ

I hope it helps!

8 0

4 years ago

How is an isotope different from the standard form of a chemical element?

velikii [3]

Answer:

The standard form of a chemical element is the natural mixture of several isotopes of the same element, which is atoms with the same number of protons but different number of neutrons, while an isotope is a particular kind of atom with a definite number of neutrons.

Explanation:

A chemical element is a pure substance formed by atoms with the same atomic number (number of protons). This is because it is the number of protons what identifies an element.

For example: oxygen is a chemical element, so oxygen is formed by only atoms of oxygen, and the atomic number of those atoms is 8, because every oxygen atom has 8 protons.

Nevertheless, some atoms of oxygen, may have different number of neutrons. Isotopes are different kind of atoms of the same element, which only differ in the number of neutrons. So, some atoms of oxygen will have 8 neutrons, other 9 neutrons, and other 10 neutrons (those are the stable isotopes of oxygen).

That difference in neutrons, is generally accepted that, does not modifiy substantially the chemical properties of the element, but the mass number. So, the isotopes with more neutrons wil be heavier, and the isotopes with less neutrons will be lighter.

Mass number = number of protons + number of neutrons.

In general a chemical element is formed by a mixutre of isotopes of the same element.

4 0

3 years ago

Read 2 more answers

HELP! Give the molar mass of Copper (II) Hydroxide.

yarga [219]

Answer:

97.561 g/mol

Explanation:

8 0

3 years ago

What are some similarities between space and earth pollution?

yawa3891 [41]

Both are caused by human ignorance. Both have the ability to kill those in them. Both can become compact to create new material.

5 0

4 years ago

Why do living things need carbon

soldier1979 [14.2K]

Animals use oxygen to convert this food into energy they can use, and to maintain a steady supply of carbon atoms that are necessary for building any animal cells. Respiration also returns carbon dioxide back to the atmosphere as a waste product, where plants can reabsorb it in the process of photosynthesis. hope I helped.

8 0

3 years ago