1. I am a solution with a pOH of 6. What am I?

determine the frequency and wavelength (in nm) of the light emitted when the e- fell from n=4 and n=2

Lostsunrise [7]

Answer:

Frequency = 6.16 ×10¹⁴ Hz

λ = 4.87×10² nm

Explanation:

In case of hydrogen atom energy associated with nth state is,

En = -13.6/n²

For n = 2

E₂ = -13.6 / 2²

E₂ = -13.6/4

E₂ = -3.4 ev

Kinetic energy of electron = -E₂ = 3.4 ev

For n = 4

E₄ = -13.6 / 4²

E₄ = -13.6/16

E₄ = -0.85 ev

Kinetic energy of electron = -E₄ = 0.85 ev

Wavelength of radiation emitted:

E = hc/λ = E₄ - E₂

hc/λ = E₄ - E₂

by putting values,

6.63×10⁻³⁴Js × 3×10⁸m/s / λ = -0.85ev - (-3.4ev )

6.63×10⁻³⁴ Js× 3×10⁸m/s / λ = 2.55 ev

λ = 6.63×10⁻³⁴ Js× 3×10⁸m/s /2.55ev

λ = 6.63×10⁻³⁴ Js× 3×10⁸m/s /2.55× 1.6×10⁻¹⁹ J

λ = 19.89 ×10⁻²⁶ Jm / 2.55× 1.6×10⁻¹⁹ J

λ = 19.89 ×10⁻²⁶ Jm / 4.08×10⁻¹⁹ J

λ = 4.87×10⁻⁷ m

m to nm:

4.87×10⁻⁷ m ×10⁹nm/1 m

4.87×10² nm

Frequency:

Frequency = speed of electron / wavelength

by putting values,

Frequency = 3×10⁸m/s /4.87×10⁻⁷ m

Frequency = 6.16 ×10¹⁴ s⁻¹

s⁻¹ = Hz

Frequency = 6.16 ×10¹⁴ Hz

3 0

3 years ago

How many moles of Al would be produced from 20 moles of Al2O3? 2Al2O3 -> 4A1 + 302

Evgesh-ka [11]

<h3>Answer:</h3>

$\displaystyle 40 \ mol \ Al$

<h3>General Formulas and Concepts:</h3>

Math

Pre-Algebra

Order of Operations: BPEMDAS

Brackets
Parenthesis
Exponents
Multiplication
Division
Addition
Subtraction

Left to Right

Chemistry

Stoichiometry

Using Dimensional Analysis

<h3>Explanation:</h3>

Step 1: Define

[RxN - Balanced] 2Al₂O₃ → 4Al + 3O₂

[Given] 20 mol Al₂O₃

Step 2: Identify Conversions

[RxN] 2 mol Al₂O₃ → 4 mol Al

Step 3: Stoich

[DA] Set up: $\displaystyle 20 \ mol \ Al_2O_3(\frac{4 \ mol \ Al}{2 \ mol \ Al_2O_3})$
[DA] Multiply/Divide [Cancel out units]: $\displaystyle 40 \ mol \ Al$

Step 4:Check

Follow sig fig rules and round. We are given 1 sig fig.

Since our final answer already has 1 sig fig, there is no need to round.

4 0

3 years ago

ch sulfide (ZnS) occurs in the zinc blende crystal structure, (a) If 254 g of ZnS contains 170 g of Zn, what is the mass ratio o

Aleonysh [2.5K]

Answer:

The mass ratio of zinc to sulfide is 85:42.

2.5559 kg of Zn are in 3.82 kg of ZnS.

Explanation:

a) Mass of zinc sulfide = 254 g

Mass of zinc in a zinc sulfide sample = 170 g

Mass of sulfide in zinc sulfide sample = x

254 g = 170 g+ x

x = 84 g

The mass ratio of zinc to sulfide:

$\frac{170 g}{84 g}=\frac{85}{42}$

b) Mass of zincsulfide sample = 3.83 kg

The mass ratio of zinc to sulfide is 85:42.

Let the mass of zinc and sulfide be 85x and 42x respectively:

85 x+ 42 x=3.82 kg

x =0.03007 kg

Mass of an zinc= 85x=85 × 0.03007 kg= 2.5559 kg

8 0

3 years ago

How many moles of water as a gas can be formed 2.45 L

Alex17521 [72]

Answer:

0.11mole

Explanation:

Let us assume that the condition is at standard temperature and pressure(STP);

Given parameters:

Volume of water = 2.45L

Unknown:

Number of moles found in this volume of water = ?

Solution;

At STP;

Number of moles = $\frac{volume of gas}{22.4}$

Input the parameters and solve;

Number of moles of water = $\frac{2.45}{22.4}$ = 0.11mole

The number of moles of water found is 0.11mole

4 0

3 years ago

The substance argon has the following properties: normal melting point: 83.9 K normal boiling point: 87.4 K triple point: 0.68 a

Vsevolod [243]

Answer:

The final state of the substance is a gas.

The sample is initially a liquid. One or more phase changes will occur.

Explanation:

Let's consider the phase diagram for Argon (not to scale).

A sample of argon is initially at a pressure of 49.6 atm and a temperature of 101.4 K. The pressure on the sample is reduced to 0.680 atm at a constant temperature of 101.4 K. Which of the following are true? Choose all that apply

The final state of the substance is a gas. TRUE. At 0.680 atm and 101.4 K, the substance is a gas.

The gas initially present will solidify. FALSE. Initially, Ar is present as a liquid.

The final state of the substance is a solid. FALSE.

The sample is initially a liquid. One or more phase changes will occur. TRUE. The sample is initially liquid and only one phase change will occur.

5 0

3 years ago