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3 years ago

22 points!

Chemistry

1 answer:

olya-2409 [2.1K]3 years ago

4 0

Answer:

The second picture is the representation of chemical change.

Explanation:

The first picture shows the physical change because in this case heat is supplied to the molecules and they move away from each others without changing the composition. It is just like the transformation of liquid water into gas. when the water is heated it evaporated without changing the composition. While the second image shows the chemical change because two substance are combined and form a new substance. Which is different from the reactants.

Chemical:

The changes, that occur due to change in the composition of a substance and result in a different compound is known as chemical change.

These changes are irreversible

These changes occur due to chemical reactions

Example:

Combustion of fuel or wood: that oil or wood convert into energy, CO2 and ash in case of wood

Boiling of egg: that change the chemical composition of protein in the egg

Physical Change

The changes that occur only due to change in shape or form but their chemical or internal composition remain unchanged.

These changes were reversible.

They have same chemical property.

Example

Water converting to Ice

Water converting to gas

In this water molecule remain the same only they rearrange themselves that change its state of mater not composition

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Which temperature and pressure are used as standards for gases?

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Answer:

0°C and 1 atm

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This are the conditions of temperature and pressure defined by IUPAC as standard.

But also, the definition used by the NIST considerates a temrperature of 20°C and a pressure of 1 atm

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1) When solid Fe metal is put into an aqueous solution of NiSO4, solid Ni metal and a solution of FeSO4 result. Write the net io

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Fe + NiSO4 ----> FeSO4 + No

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An oxide of nitrogen contains 30.45 mass % N.

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An oxide of nitrogen contains 30.45 mass % N, if the molar mass is 90± 5 g/mol the molecular formula is N₂O₄.

<h3>What is molar mass?</h3>

The molar mass of a chemical compound is determined by dividing its mass by the quantity of that compound, expressed as the number of moles in the sample, measured in moles. A substance's molar mass is one of its properties. The compound's molar mass is an average over numerous samples, which frequently have different masses because of isotopes.

<h3>How to find the molecular formula?</h3>

The whole-number multiple is defined as follows.

Whole-number multiple = $\frac{molar mass (g/mol)}{empirical formula mass (g/mol)}$

The empirical formula mass is shown below.

Mw of empirical formula = Mw of N+ 2 x (Mw of O)

= 14.01 g/mol + 2 x (16.00 g/mol)

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With the given molar mass or the molecular formula mass, we can get the whole-number multiple for the compound.

Whole-number multiple = $\frac{90 g/mol }{46.01 g/mol}$ ≈ 2

Multiplying the subscripts of NO2 by 2, the molecular formula is N(1x2)O(2x2)= N2O4.

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1 year ago

Arrhenius base definition

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3 years ago

A mixture containing 20 mole % butane, 35 mole % pentane and rest

notka56 [123]

Answer:

2.5 % butane, 42.2 % pentane and 55.3 % hexane

Explanation:

Hello,

In this case, the mass balance for each substance is given by:

$Butane:z_bF=y_bD+x_bB\\\\Pentane: z_pF=y_pD+x_pB\\\\Hexane: z_hF=y_hD+x_hB$

Whereas $y$ accounts for the fractions at the outlet distillate and $x$ for the fractions at the outlet bottoms. Moreover, with the 90 % recovery of butane, we can write:

$0.9=\frac{y_bD}{z_bF}$

So we can compute the product of the molar fraction of butane at the distillate by total distillate flow by assuming a 100-mol feed:

$y_bD=0.9*z_bF=0.9*0.2*100mol=18mol$

The total distillate flow:

$y_bD=18mol\\\\D=\frac{18mol}{0.95} =18.95mol$

And the total bottoms flow:

$F=D+B\\\\B=F-D=100mol-18.95mol=81.05mol$

Next, by using the mass balance of butane, we compute the molar fraction of butane at the bottoms:

$x_b=\frac{z_bF-y_bD}{B} =\frac{0.2*100mol-18mol}{81.05} =0.025$

Then, the molar fraction of pentane and hexane:

$x_p=\frac{z_pF-y_pD}{B} =\frac{0.35*100mol-0.04*18.95mol}{81.05} =0.422$

$x_h=\frac{z_hF-y_hD}{B} =\frac{(1-0.2-0.35)*100mol-(1-0.95-0.04)*18.95mol}{81.05} =0.553$

Therefore, the molar composition of the bottom product is 2.5 % butane, 42.2 % pentane and 55.3 % hexane.

NOTE: notice the result is independent of the value of the assumed feed, it means that no matter the basis, the compositions will be the same for the same recovery of butane at the feed, only the flows will change.

Regards.

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