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1 year ago

1. Differentiate Physical and chemical changes of matter?

1 answer:

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In a physical change the appearance or form of the matter changes but the kind of matter in the substance does not. However in a chemical change, the kind of matter changes and at least one new substance with new properties is formed.

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What does an emission spectrum show?

IrinaVladis [17]

It shows the type of atoms/elements in a substance

Different types of atoms have different emission spectrum - a concept supported by Bohr quantum theory - hence one is able to identify elements in a substance using a method called spectroscopy.

Explanation:

When an electron jumps from a low energy orbital to a higher energy orbital in an atom, it absorbs a specific wavelength of electromagnetic radiation (This is called absorption spectrum). Vice versa, if the same electron jumps from a higher to a lower energy orbital it releases the equivalent quantum energy in electromagnetic wave (This is called emission spectrum). Different types of atoms of different elements have a unique spectrum identifier.

Learn More:

Learn more about spectroscopy;

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2 years ago

Lattice energy is Question 4 options: the energy given off when gaseous ions combine to form one mole of an ionic solid the ener

aleksley [76]

Answer:

Lattice energy is <em>the energy required to convert a mole of ionic solid into its constituent ions in the gas phase</em>

Explanation:

Lattice energy is usually calculated by the Born-Haber cycle, from the affinity energies and sublimation ethalphy values. It is used as an estimation of the ionic energy strength between the ions in an ionic compound.

It is defined as the energy needed to broke 1 mol of a given ionic compound into its ions in the gaseous state. For example, the lattice energy for sodium chloride (NaCl) is the energy required to separate 1 mol of solid ionic compound (NaCl(s)) and produce the sodium and chlorine ions in the gas phase: Na⁺(g) and Cl⁻(g).

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2 years ago

A decentralized system of crime laboratories currently exists in the United States under the auspices of various governmental ag

Vesna [10]

Answer:

Federal, State, Municipal and County

Explanation:

A decentralized system of crime laboratories currently exists in the United States under the auspices of various governmental agencies at the federal, state, municipal and county levels of government.

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3 years ago

What is the total energy change for the following reaction:CO+H2O-CO2+H2

Alekssandra [29.7K]

Answer:

$\large \boxed{\text{-41.2 kJ/mol}}$

Explanation:

Balanced equation: CO(g) + H₂O(g) ⟶ CO₂(g) + H₂(g)

We can calculate the enthalpy change of a reaction by using the enthalpies of formation of reactants and products

$\Delta_{\text{rxn}}H^{\circ} = \sum \left( \Delta_{\text{f}} H^{\circ} \text{products}\right) - \sum \left (\Delta_{\text{f}}H^{\circ} \text{reactants} \right)$

(a) Enthalpies of formation of reactants and products

$\begin{array}{cc}\textbf{Substance} & \textbf{$\Delta_{\text{f}}$H/(kJ/mol}) \\\text{CO(g)} & -110.5 \\\text{H$_{2}$O} & -241.8\\\text{CO$_{2}$(g)} & -393.5 \\\text{H$_{2}$(g)} & 0 \\\end{array}$

(b) Total enthalpies of reactants and products

$\begin{array}{ccr}\textbf{Substance} & \textbf{Contribution)/(kJ/mol})&\textbf{Sum} \\\text{CO(g)} & -110.5& -110.5 \\\text{H$_{2}$O(g)} &-241.8& -241.8\\\textbf{Total}&\textbf{for reactants} &\mathbf{ -352.3}\\&&\\\text{CO}_{2}(g) & -393.5&-393.5 \\\text{H}_{2} & 0 & 0\\\textbf{Total}&\textbf{for products} & \mathbf{-393.5}\end{array}$

(c) Enthalpy of reaction $\Delta_{\text{rxn}}H^{\circ} = \sum \left( \Delta_{\text{f}} H^{\circ} \text{products}\right) - \sum \left (\Delta_{\text{f}}H^{\circ} \text{reactants} \right)= \text{-393.5 kJ/mol - (-352.3 kJ/mol}\\= \text{-393.5 kJ/mol + 352.3 kJ/mol} = \textbf{-41.2 kJ/mol}\\ \text{The total enthalpy change is $\large \boxed{\textbf{-41.2 kJ/mol}}$}$

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2 years ago

What do they mean by “zigzag line” ?

Dafna11 [192]

Answer:

A zigzag is a line that has a series of angles in it like a continuous series of 'W's. They staggered in a zigzag across the tarmac. ... a zigzag pattern.

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2 years ago