Salt dissolving in water is a physical change. (2 points) True False

Describe how light is emitted from an atom. A) As protons absorb energy they travel from the nucleus through the atom emitting l

vovangra [49]

Answer is: D) Light is emitted from an atom as an electron falls from an excited state to the ground state releasing a photon.

Electrons can jump from one energy level to another, absorbing or emitting electromagnetic radiation with a frequency ν (energy difference of the levels).

When electron jump from higher to lower energy level (shell), it emitting (releasing) energy.

For example, when the electron changes from n=4 (fouth shell) to n=2 (second shell), the photons are emitted.

Albert Einstein (1879-1955) proposed that a beam of light is a collection of discrete wave packets (photons) with energy hν, where h is Planck constant and ν is frequency.

The photons have a characteristic energy proportional to the frequency of the light.

Minimum frequency or the threshold frequency is energy below which no photoelectrons are emitted.

Above the minimum frequency, energy depends on the frequency of the light, not on the intensity of the light.

7 0

3 years ago

A solution of sodium chloride in water has a vapor pressure of 19.6 torr at 25°C. What is the mole fraction of NaCl in this solu

Debora [2.8K]

Answer:

Mole fraction of Nacl is 0.173

Explanation:

we know that

$P_{sol}=\chi_{solvent}P^0_{solvent}$

where,

P sol - the vapor pressure of the solution

χ solvent - the mole fraction of the solvent

P ∘ solvent - the vapor pressure of the pure solvent

This means that in order to be able to calculate the mole fraction of sodium chloride, you need to know what the vapor pressure of pure water is at

25 ° C You can use an online calculator to find that the vapor pressure of pure water at 25 C is equal to about 23.8 torr .

$\chi_{water}= \frac{P{sol}}{P^0{water}}$

$\chi_{water}= \frac{19.6}{23.8}$

=0.827

Also we know that

$\chi_{water}+\chi_{Nacl}= 1$

This means that the mole fraction of sodium chloride is

χ_{Nacl}= 1-Χ_{water}

= 1-0.827 =0.173

3 0

3 years ago

What is the name of the binary molecule H2O2? This compound is also known as hydrogen peroxide and is a properly disinfectant or

Masteriza [31]

Answer:

hydrogen dioxide

Explanation:

3 0

4 years ago

A sample of CO2 weighing 86.34g contains how many molecules?

irakobra [83]

Answer:

1.181 × 10²⁴ molecules CO₂

General Formulas and Concepts:

Chemistry - Atomic Structure

Reading a Periodic Table
Using Dimensional Analysis
Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Explanation:

Step 1: Define

86.34 g CO₂

Step 2: Identify Conversion

Avogadro's Number

Molar Mass of C - 12.01 g/mol

Molar Mass of O - 16.00 g/mol

Molar Mass of CO₂ - 12.01 + 2(16.00) = 44.01 g/mol

Step 3: Convert

$86.34 \ g \ CO_2(\frac{1 \ mol \ CO_2}{44.01 \ g \ CO_2} )(\frac{6.022 \cdot 10^{23} \ molecules \ CO_2}{1 \ mol \ CO_2} )$ = 1.18141 × 10²⁴ molecules CO₂

Step 4: Check

We are given 4 sig figs. Follow sig fig rules and round.

1.18141 × 10²⁴ molecules CO₂ ≈ 1.181 × 10²⁴ molecules CO₂

4 0

3 years ago

10.0 g of calcium carbonate was heated. The mass of calcium oxide left was 5.6 g. Calculate the mass of

Kipish [7]

Answer:

4.4g

Explanation:

Mass of CaCO3 = 10g

Mass of CaO = 5.6g

Mass of CO2 =?

Mass of CaCO3 = Mass of CaO + Mass of CO2

Mass of CO2 = Mass of CaCO3 — Mass of CaO

Mass of CO2 = 10 — 5.6

Mass of CO2 = 4.4g

4 0

3 years ago

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