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3 years ago

Classify each of the following changes as Physical or Chemical:

Chemistry

1 answer:

ddd [48]3 years ago

6 0

Explanation:

Physical changes are the changes that does not lead to any change in chemical composition of a substance.

For example, mass, density, volume are all physical changes.

On the other hand, a change that leads to formation of a new compound by changing the chemical composition of reactants or combining atoms is known as a chemical change.

For example, combustion, toxicity, reactivity etc are all chemical changes.

Therefore, given changes are identified as follows.

Coal burning : It is a combustion reaction. Hence, it is a chemical change.

Ice melting : Physical state of water changes from solid to liquid. Hence, it is a physical change.

mixing chocolate syrup with milk : No new compound is forming as there is no chemical reaction occurring. Hence, it is also a physical change.

explosion of a firecracker : It shows reactivity of fire cracker. Hence, it is a chemical reaction.

magnetizing of a screwdriver : It shows physical attraction between the magnet and screwdriver. Hence, it is a physical change.

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Rank the following elements by electron affinity, from most positive to most negative EA value. Rank from most positive to most

Svetlanka [38]

Answer:

Most positive = rubidium

Most negative = fluorine

Explanation:

Electron affinity of an element is the energy released when an electron is attached to a neural atom to form an ion in its gaseous state.

X + e⁻ → X⁻

Electron affinity is similar to electronegativity which is the tendency at which an atom accepts an ion towards itself.

Electron affinity increases across the period and decreases down the group in the periodic table.

In the above option,

Fluorine has the highest electron affinity

Rubidium has the lowest electron affinity

Tellurium and then finally Phosphorus

Helium in this case would have the lowest electron affinity because it has filled orbital and does not require any electron to attain stability. Technically, Helium has the lowest or is expected to have the lowest electron affinity which is close to zero according to quantum mechanics.

Most positive = rubidium

Most negative = fluorine.

You can check periodic table for their exact values

6 0

4 years ago

What is the energy of light with a wavelength of 468 nm? (The speed of light

marshall27 [118]

The answer for the problem is explained below.

The option for the answer is "D".

Therefore the energy of the light is 4.25 × 10^-19 J

Explanation:

Given:

wavelength (λ) = 468 nm = 468×10^-9 m

speed of light (c) = 3.00 x 10^8m/s

Planck's constant is 6.626 x 10^-34J·s

To solve:

energy of light (E)

We know,

E =(h×c) ÷ λ

E = ( 6.626 x 10^-34 × 3.00 x 10^8) ÷ 468×10^-9

E = 4.25 × 10^-19 J

Therefore the energy of the light is 4.25 × 10^-19 J

6 0

3 years ago

Butane C4H10 (g),(Hf = –125.7), combusts in the presence of oxygen to form CO2 (g) (Delta.Hf = –393.5 kJ/mol), and H2O(g) (Delta

shusha [124]

Answer: The enthalpy of combustion, per mole, of butane is -2657.4 kJ

Explanation:

The balanced chemical reaction is,

$2C_4H_{10}(g)+13O_2(g)\rightarrow 8CO_2(g)+10H_2O(g)$

The expression for enthalpy change is,

$\Delta H=[n\times H_f_{products}]-[n\times H_f_{reactants}]$

Putting the values we get :

$\Delta H=[8\times H_f_{CO_2}+10\times H_f_{H_2O}]-[2\times H_f_{C_4H_{10}+13\times H_f_{O_2}}]$

$\Delta H=[(8\times -393.5)+(10\times -241.82)]-[(2\times -125.7)+(13\times 0)]$

$\Delta H=-5314.8kJ$

2 moles of butane releases heat = 5314.8 kJ

1 mole of butane release heat = $\frac{5314.8}{2}\times 1=2657.4kJ$

Thus enthalpy of combustion per mole of butane is -2657.4 kJ

3 0

3 years ago

Write the formulas of the following compounds:

dem82 [27]

Answer:

a) Li2CO3

b) NaCLO4

c) Ba(OH)2

d) (NH4)2CO3

e) H2SO4

f) Ca(CH3COO)2

g) Mg3(PO4)2

f) Na2SO3

Explanation:

a) 2Li + CO3 ↔ Li2CO3

b) NaOH * HCLO4 ↔ NaCLO4 + H2O

c) Ba + 2H2O ↔ Ba(OH)2 +

d) 2NH4 + H2CO3 ↔ (NH4)2CO3 + H2O

c) SO2 + NO2 +H2O ↔ H2SO4 + NOx

f) 2CH3COOH + CaO ↔ Ca(CH3COOH)2 + H2O

g) 3MgO + 2H3PO4 ↔ Mg3(PO4)2 + H2O

h) NaOH + H2SO3 ↔ Na2SO3 + H2O

6 0

3 years ago

When electricity flows through water, the water molecules split into molecules of hydrogen and oxygen gas. How many oxygen (O2)

ikadub [295]

That would be one oxygen molecule.

5 0

3 years ago

Read 2 more answers