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3 years ago

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modern atomic theory is on_____including Dalton's atomic theory and quantum mechanics, Modern atomic theory is built on es -)) A

) Bohr B) nuclear C) plum pudding D) previous models

1 answer:

musickatia [10]3 years ago

7 0

Answer:

D) Previous models

Got it right on USTestPrep

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An unknown substance is heated from 10 °C to 25 °C. The table below shows the state of the substance at different temperatures.

bezimeni [28]

Answer:

Its melting point is 17 °C.

Explanation:

The melting point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium.

<em>So, the melting point is 17 °C.</em>

And this is shown in the figure attached.

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3 years ago

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Tamara is studying the human digestive system in science class. A diagram similar to the one that follows appears in her text bo

grin007 [14]

Answer:

esophagus

Explanation:

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3 years ago

All of the following statements are correct except The conversion of compounds into elements is a chemical change. The conversio

aleksandrvk [35]

Answer:

The conversion of liquid water into gaseous water is a chemical change

Explanation:

A chemical change occurs when there is a chemical reaction, so there'll be changed in the compounds, such as forming new ones, forming its elements, or elements forming compounds.

A physical change occurs when there is a change in the state of aggregation of the compound, it means that it changes its physical state. Solid for liquid, liquid for solid, liquid for gas, gas for liquid, solid for gas, and gas for solid are the physical changes.

So the evaporation of water, or its conversion in gaseous water, is a physical change, not a chemical change.

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3 years ago

A microwave can have a frequency of 3.8 X 1010Hz. How much energy does this microwave give off in joules?

Marina86 [1]

Answer:

2.52 x $10^{-23}$ J

Explanation:

The energy given off by the microwave can be determined by the application of Planck's energy formula:

E = hf

where: E is the required energy, h is Planck's constant (6.626 x $10^{-34}$ $m^{2}$ Kg/s), and f is the frequency (3.8 x $10^{10}$ Hz).

So that;

E = 6.626 x $10^{-34}$ x 3.8 x $10^{10}$

= 2.51788 x $10^{-23}$

Therefore, the energy released by the wave is 2.52 x $10^{-23}$ J.

3 0

3 years ago

A sample of sodium sulfite has a mass of 2.80 g.

Gnom [1K]

<u>Answer:</u>

<u>For a:</u> The number of sodium ions in given amount of sodium sulfite are $2.65\times 10^{22}$

<u>For b:</u> The number of sulfite ions in given amount of sodium sulfite are $1.325\times 10^{22}$

<u>For c:</u> The mass of one formula unit of sodium ions is $2.09\times 10^{-22}$ grams

<u>Explanation:</u>

The chemical formula of sodium sulfite is $Na_2SO_3$ . It is formed by the combination of 2 sodium $(Na^+)$ ions and 1 sulfite $(SO_3^{2-})$ ions

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of sodium sulfite = 2.80 g

Molar mass of sodium sulfite = 126 g/mol

Putting values in above equation, we get:

$\text{Moles of sodium sulfite}=\frac{2.80g}{126g/mol}=0.022mol$

<u>For a:</u>

Moles of sodium ions in sodium sulfite = (2 × 0.022) moles

According to mole concept:

1 mole of a compound contains $6.022\times 10^{23}$ number of particles

So, 0.022 moles of sodium sulfite will contain = $(2\times 0.022\times 6.022\times 10^{23})=2.65\times 10^{22}$ number of sodium ions

Hence, the number of sodium ions in given amount of sodium sulfite are $2.65\times 10^{22}$

<u>For b:</u>

Moles of sulfite ions in sodium sulfite = (1 × 0.022) moles

According to mole concept:

1 mole of a compound contains $6.022\times 10^{23}$ number of particles

So, 0.022 moles of sodium sulfite will contain = $(1\times 0.022\times 6.022\times 10^{23})=1.325\times 10^{22}$ number of sulfite ions

Hence, the number of sulfite ions in given amount of sodium sulfite are $1.325\times 10^{22}$

<u>For c:</u>

Molar mass of sodium sulfite = 126 g/mol

According to mole concept:

$6.022\times 10^{23}$ number of formula units are present in 1 mole of a compound

Or, $6.022\times 10^{23}$ number of formula units of sodium sulfite have a mass of 126 grams

So, 1 formula unit of sodium sulfite will have a mass of = $\frac{126}{6.022\times 10^{23}}\times 1=2.09\times 10^{-22}g$

Hence, the mass of one formula unit of sodium ions is $2.09\times 10^{-22}$ grams

7 0

3 years ago