Chemistry, 21.09.2019 04:30 evansh78

Why does a salt compound give off light (or a colored flame) when burned? 4. did lithium chloride and sodium chloride give off similar colors? why or why not? 5. explain what you think causes different compounds to give off different flame colors. 6. using your results, identify which substances you would put in a firework to delight a crowd of spectators?

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Answer from: ovebrown

The salt compounds give off light due to their emission spectrum.

(4) $\boxed{{\text{No}}}$ , lithium chloride and sodium chloride do not give off similar colors because of the difference in their emission spectrum.

(5) Flame colors are characteristics of $\boxed{{\text{energy difference}}}$ between the two levels, which is different for different elements.

(6) $\boxed{{\text{Salts of alkali and alkaline earth metals}}}$ can be put in a firework.

Further explanation:

Electronic transition:

An electronic transition is a process that occurs when an electron undergoes emission or absorption from one energy level to another energy level.

When an electron undergoes a transition from lower energy level to the higher energy level then it requires energy to complete the process. This transition is an absorption process.

When an electron undergoes a transition from higher energy level to lower energy level then it emits energy to complete the process. This transition is an emission process.

The formula to calculate the difference between two energy levels of an atom is,

$\Delta E={R_{\text{H}}}\left({\frac{1}{{{{\left({{{\text{n}}_{\text{i}}}}\right)}^2}}}-\frac{1}{{{{\left({{{\text{n}}_{\text{f}}}}\right)}^2}}}}\right)$

Where,

$\Delta E$ is the energy difference between two energy levels.

${R_{\text{H}}}$ is Rydberg constant.

${{\text{n}}_{\text{i}}}$ is the initial energy level of transition.

${{\text{n}}_{\text{f}}}$ is the final energy level of transition.

The salt compound gives off the light because its electrons absorb energy and get excited to some higher energy level. But when it returns to the lower level, it emits energy in the form of light, resulting in emission spectrum.

(4) No, lithium chloride and sodium chloride do not give off similar colors. This is because both these compounds have different allowed energy levels for their respective electrons. Lithium ion shows a red emission spectrum while sodium ion shows yellow emission spectrum.

(5) Different elements have different allowed energy levels for electrons. When an atom is heated, it absorbs energy and reaches some higher energy level. When an electron jumps from higher energy level to lower energy level, it emits energy in form of light. The wavelength of light depends on the energy difference between the two levels, which is different for different elements, and therefore different elements show different flame colors.

(6) Salts of alkali and alkaline earth metals can be used in fireworks as these are highly electropositive metals and give off electrons so easily and bright colored flames are produced. For example, barium chloride gives off the green flame when burned.

Learn more:

1. Component of John Dalton’s atomic theory:

2. Basis of investigation for the scientists:

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Atomic structure

Keywords: electronic transition, barium chloride, colored flames, alkali, alkaline earth metals, electropositive, emission, absorption, electrons, allowed energy levels, higher level, lower level.

Answer from: Quest

the formula for the conversion of temperature from degree celsius to kelvin is:

$k = ^{o}c + 273.15$

the sample of water at $38^{o}c$ is converted to kelvin temperature by using the above formula as:

$k = 38^{o}c + 273.15 = 311.15 k$

on comparing the two samples of water at $38^{o}c$ or we can say that at $311.15 k$ and at $295 k$ respectively. the difference between the temperatures of two samples of water is: