The periodic table displaysOA. all of the known elements that exist in the world today.
OB. only the important elements that exist in the world.
OC. only the important compounds that exist in the world.

Answers

Answer 1

Answer:

OA. all the known elements that exist in the world today.

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The destruction of the ozone layer by chlorofluorocarbons (CFC’s) can be described by the following reactions:ClO(g) + O3(g) ? Cl(g) + 2 O2(g) ?H°rxn = –29.90 kJ2 O3(g) ? 3 O2(g) ?H°rxn = 24.18 kJDetermine the value of heat of reaction for the following:Cl(g) + O3(g) ? ClO(g) + O2(g) ?H°=_____________?

Answers

Answer:

ΔH°rxn = 54.08 kJ

Explanation:

Let's consider the following equations.

a) ClO(g) + O₃(g) ⇄ Cl(g) + 2 O₂(g) ΔH°rxn = –29.90 kJ

b) 2 O₃(g) ⇄ 3 O₂(g) ΔH°rxn = 24.18 kJ

We have to determine the value of heat of reaction for the following reaction: Cl(g) + O₃(g) ⇄ ClO(g) + O₂(g)

According to Hess's law, the enthalpy change in a chemical reaction is the same whether the reaction takes place in one or in several steps. That means that we can find the enthalpy of a reaction by adding the corresponding steps and adding their enthalpies. According to Lavoisier-Laplace's law, if we reverse a reaction, we also have to reverse the sign of its enthalpy.

Let's reverse equation a) and add it to equation b).

-a) Cl(g) + 2 O₂(g) ⇄ ClO(g) + O₃(g) ΔH°rxn = 29.90 kJ

b) 2 O₃(g) ⇄ 3 O₂(g) ΔH°rxn = 24.18 kJ

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Cl(g) + 2 O₂(g) + 2 O₃(g) ⇄ ClO(g) + O₃(g) + 3 O₂(g)

Cl(g) + O₃(g) ⇄ ClO(g) +O₂(g)

ΔH°rxn = 29.90 kJ + 24.18 kJ = 54.08 kJ

Final answer:

The heat of the reaction (ΔH°rxn) for the reaction Cl(g) + O3(g) ? ClO(g) + O2(g) is calculated using Hess's Law. The sum of the heat of reversed first reaction and the second reaction provided is 54.08 kJ.

Explanation:

The chemistry question asks to determine the heat of the reaction for the reaction Cl(g) + O3(g) ? ClO(g) + O2(g). In Hess's Law, the heat of the reaction or ΔH for a reaction can be calculated from the sum of the heats of other reactions that sum to the desired reaction. In this case, we want to reverse the first reaction provided (which changes the sign of ΔH) and add it to the second reaction provided.

So, reversing the first reaction we get: Cl(g) + 2 O2(g) ? ClO(g) + O3(g) ?H°rxn = 29.90 kJ

Adding this to the second reaction: 2 O3(g) ? 3 O2(g), ?H°rxn = 24.18 kJ, gives the reaction Cl(g) + O3(g) ? ClO(g) + O2(g). Adding the ΔH values gives the ΔH for this reaction: 29.90 kJ + 24.18 kJ = 54.08 kJ. So, ?H°rxn for the reaction Cl(g) + O3(g) ? ClO(g) + O2(g) is 54.08 kJ.

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Compute the repeat unit molecular weight of polystyrene. (b) Compute the number-average molecular weight for a polystyrene for which the degree of polymerization is 23000.

Answers

Answer :

(a) The repeat unit is, styrene

(b) The number-average molecular weight is, 2392000 g/mol

Explanation :

First we have to calculate the repeat unit molecular weight of polystyrene.

As, the repeat unit is, styrene having chemical formula $C_8H_8$

Molecular weight of repeat unit = 8 × C + 8 × H

Molecular weight of repeat unit = 8 × 12 g/mol + 8 × 1 g/mol

Molecular weight of repeat unit = 104 g/mol

Now we have to calculate the number-average molecular weight.

Number-average molecular weight = Average repeat molecular weight × Degree of polymerization

Number-average molecular weight = (104 g/mol) × (23000)

Number-average molecular weight = 2392000 g/mol

Thus, the number-average molecular weight is, 2392000 g/mol

Final answer:

The repeat unit molecular weight of polystyrene is 104.15 g/mol. The average molecular weight of polystyrene with a polymerization degree of 23000 is approximately 2,395,450 g/mol.

Explanation:

To answer this question, we first need to understand that the repeating unit in polystyrene is the styrene monomer, which is C8H8. The molecular weight of this unit can be calculated by adding up the atomic weights of all the atoms in the monomer. The atomic weights of carbon (C), hydrogen (H), and styrene-based on the periodic table are approximately 12.01 amu, 1.01 amu, and 104.15 g/mol respectively. This gives a total of 104.15 g/mol for the repeat unit molecular weight of polystyrene.

Given that the degree of polymerization is 23000, we can calculate the number-average molecular weight by multiplying the repeat unit molecular weight (104.15 g/mol) by the degree of polymerization (23000). This gives a total of approximately 2,395,450 g/mol for the number-average molecular weight.

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Scaled Synthesis of Alum. Show your calculations for:a.the experimental scaling factor giving rise to a 15.0 g theoretical yield;b.the corrected volumes of KOH and H2SO4; andc.the theoretical yield of alum based on the actual amount of Al used.Make sure you carefully show each step for these calculations.

Answers

Answer:

Explanation:

You don't give your experimental data, so I shall assume:

Mass of Al = 1.07 g

20 mL of 3 mol·L⁻¹ KOH

20 mL of 9 mol·L⁻¹ H₂SO₄

The overall equation for the reaction is

Mᵣ: 26.98 474.39

2Al + 2KOH +4H₂SO₄ + 22H₂O ⟶ 2K[Al(SO₄)₂]·12H₂O + 3H₂

m/g: 1.07

(c) Theoretical yield of alum

(i) Moles of Al

$\text{Moles of Al} = \text{1.07 g Al} * \frac{\text{1 mol Al}}{\text{26.98 g Al}} = \text{0.039 66 mol Al}$

(ii) Moles of alum

$\text{Moles of alum} = \text{0.039 66 mol Al} * \frac{\text{2 mol alum }}{\text{2 mol Al}} = \text{0.039 66 mol alum \n}$

(iii) Theoretical yield of alum

$\text{Mass of alum} = \text{0.039 66 mol alum} * \frac{\text{474.39 g alum}}{\text{1 mol alum}} = \textbf{18.8 g alum}$

(a) Scaling factor for 15.0 g alum

You want a theoretical yield of 15.0 g, so you must scale down the reaction.

$\text{Scale factor} = (15.0)/(18.8) = \mathbf{0.798}$

(b) Corrected volumes of NaOH and H₂SO₄

V = 0.798 × 20 mL = 16 mL

What is the independent variable of the penny lab

Answers

The independent variable in the experiment is the soap and the dependent variable in the experiment is the number of water drops on the surface of the penny. The control is the penny without soap.

A cylinder is filled with 10.0L of gas and a piston is put into it. The initial pressure of the gas is measured to be 96.0kPa. The piston is now pulled up, expanding the gas, until the gas has a final volume of 45.0L. Calculate the final pressure of the gas. Be sure your answer has the correct number of significant digits.