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3 years ago

Classify each of the following as an element, a compound, or a mixture:

Chemistry

2 answers:

mote1985 [20]3 years ago

3 0

A) an element
B) an element
C) a compound
D) a mixture
E) a compound
F) a compound
G) a compound

kobusy [5.1K]3 years ago

3 0

Explanation:

An element is defined as a substance which contains same type of atoms.

For example, a small block made up of only copper metal will contain only atoms of copper.

A compound is defined as a substance in which atoms chemically combine together in a fixed ratio by mass.

For example, HgO is a compound.

A mixture is defined as a substance in which two or more components are physically combined but none of the components are chemically combined to each other.

For example, a pan cake syrup is a mixture.

Components of a mixture can be separated by physical means.

Thus, we classify each of the given species as follows.

iron - element

oxygen - element

mercury oxide - compound

pancake syrup - mixture

carbon dioxide - compound

a substance composed of molecules each of which contains one hydrogen atom and one chlorine atom - compound

baking soda - compound

baking powder - compound

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_____________________ held that all matter is made up of four “elements”— earth, air, fire, and water.

Novosadov [1.4K]

Answer:

Democritus

Explanation:

He spoke about matter was made of tiny particles which moved in empty space

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3 years ago

What pressure is required to achieve a co2 concentration of 7.90×10−2 m at 20∘c?

Savatey [412]

Answer:- 1.90 atm

Solution:- It is based on combined gas law equation, PV = nRT

In this equation, P is pressure, V is volume, n is moles of gas, R is universal gas constant and T is kelvin temperature.

If we divide both sides by V then:

$P=\frac{nRT}{V}$

We know that, molarity is moles per liter. So, in the above equation we could replace $\frac{n}{V}$ by molarity, M of the gas. The equation becomes:

P = MRT

T = 20 + 273 = 293 K

M = $7.9*10^-^2$

Let's plug in the values in the equation:

P = $(7.9*10^-^2)(0.0821)(293)$

P = 1.90 atm

So, the pressure of the gas is 1.90 atm.

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3 years ago

Diamond is forever" is one of the most successful advertising slogans of all time. but is it true? for the reaction shown below,

Zielflug [23.3K]

The given reaction is

$C _{(Diamond)}\rightarrow C_{(Graphite)}$

An element can exist in 2 or more different forms which have totally different chemical and physical properties. They are known an allotropes.

Diamond and Graphite are allotropic forms of carbon. In the given reaction, diamond is changing to graphite and we have to find out the standard free energy of this reaction. This will help us to find out whether this reaction is spontaneous at 298 K or not.

The following data is needed for calculations which is taken from standard reference table.

$H_{f}^{0}(diamond)= 1.895 kJ/mol$

$H_{f}^{0}(graphite)= 0$

$S^{0}(diamond)=2.337 J/mol-K$

$S^{0}(graphite)=5.740 J/mol-K$

Step 1: Find ΔH⁰ rxn for the given reaction.

The formula to calculate ΔH⁰ rxn is given below.

$\bigtriangleup H^{0}_{rxn}= H_{f}(product)- H_{f}( reactant)$

We have graphite on product side and diamond on reactant side.

Therefore, $\bigtriangleup H^{0}_{rxn}= H_{f}(graphite)- H_{f}(diamond)$

Let us plug in the values given above.

$\bigtriangleup H^{0}_{rxn}= 0 - 1.895 kJ/mol$

$\bigtriangleup H^{0}_{rxn}= - 1.895 kJ/mol$

ΔH⁰ rxn for the given reaction is -1.895 kJ/mol

Step 2 : Find ΔS⁰ rxn for the given reaction.

The formula to calculate ΔS⁰ rxn is

$\bigtriangleup S^{0}_{rxn}= S^{0}(product)- S^{0}( reactant)$

$\bigtriangleup S^{0}_{rxn}= S^{0}(graphite)- S^{0}(diamond)$

$\bigtriangleup S^{0}_{rxn}= (5.740J/mol.K) - (2.337 J/mol.K)$

$\bigtriangleup S^{0}_{rxn}= 3.403 J/mol.K$

Let us convert this to kJ.

$\frac{3.403J}{mol.K}\times \frac{1 kJ}{1000J}= 3.403\times 10^{-3}kJ/mol.K$

ΔS⁰ rxn for the given reaction is 3.403 x 10⁻³ kJ/mol.K

Step 3: Find standard free energy ΔG⁰ rxn.

ΔG⁰ rxn for the given reaction is calculated as

$\bigtriangleup G^{0}_{rxn}= \bigtriangleup H^{0}_{rxn}- T\times \bigtriangleup S^{0}_{rxn}$

We have T = 298 K. Let us plug in the calculated values of ΔH⁰ rxn and ΔS⁰ rxn.

$\bigtriangleup G^{0}_{rxn}= - 1.895 kJ/mol - [(298K)\times 3.403\times 10^{-3}kJ/mol.K]$

$\bigtriangleup G^{0}_{rxn}= - 1.895 kJ/mol - [1.014 kJ/mol]$

$\bigtriangleup G^{0}_{rxn}= - 2.909 kJ/mol$

The standard free energy change for the given reaction is -2.909 kJ/mol

The negative value of delta G⁰ suggests that the given reaction is spontaneous at room temperature. That means diamond will slowly convert to graphite. The speed of this reaction is extremely slow, but yet the reaction is taking place. So over a period of time diamond will become graphite.

Therefore "Diamond is forever" is not true as it is going to get converted to graphite.

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4 years ago

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alexdok [17]

Answer:

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Explanation:

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3 years ago

Scale

Oduvanchick [21]

Answer:

7.58

Explanation:

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3 years ago