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weqwewe [10]
3 years ago
10

C (graphite) is used as a lubricant, whereas C (diamond) is used as an abrasive. Why is this?

Chemistry
1 answer:
zysi [14]3 years ago
4 0

Answer:

Carbon atoms in graphite and diamond are arranged in different ways. Hence, the two allotropes of carbon have different physical properties.

Explanation:

Both graphite and diamond are both made of only carbon atoms. However, their physical properties differ from each other. Hence, they are called allotropes. Think about how these carbon atoms are arranged in each of the allotropes.

<h3>Graphite</h3>

In graphite, each carbon atom is bonded to three other carbon atoms. These carbon atoms will be located in the same plane. A chunk of graphite can contain many of these planes.

Each carbon atom has four valence electrons. Three of these electrons will be used in the bonds. The other electron will be delocalized. These electrons would flow between the sheets of carbon atoms. That keeps the sheets separate and allow them to slide on top of each other.

<h3>Diamond</h3>

In diamond, each carbon atom is bonded to four other carbon atoms. These carbon atoms will form a tetrahedral network.  

In graphite, there's a significant separation between two adjacent sheets of carbon atoms. The force between the two sheets is rather weak. When a piece of graphite is between two objects that move over one another, the layers in the graphite would also slide over one another. Since the attraction between two adjacent sheets isn't very strong, there wouldn't be much resistance. Hence the graphite acts as a lubricant.  

In contrast, most of the carbon atoms in a piece of diamond would be connected to each other. Unlike the sheets in graphite, in a diamond there are almost no moving parts. Also, the forces between neighboring carbon atoms are very strong. When an external force acts on a chunk of diamond, the carbon atoms would barely move. Hence, the structure appears to be very rigid. That gives diamond its abrasive properties.

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A solution contains 0.115 mol h2o and an unknown number of moles of nacl. the vapor pressure of the solution at 30°c is 25.7 tor
Valentin [98]
According to Raoult's low:
We will use this formula: Vp(Solution) = mole fraction of solvent * Vp(solvent)
∴ mole fraction of solvent = Vp(Solu) / Vp (Solv)
when we have Vp(solu) = 25.7 torr & Vp(solv) = 31.8 torr 
So by substitution:
∴ mole fraction of solvent = 25.7 / 31.8 =0.808 
when we assume the moles of solute NaCl = X 
and according to the mole fraction of solvent formula:
mole fraction of solvent = moles of solvent / (moles of solvent + moles of solute)
by substitute:
∴ 0.808 = 0.115 / (0.115 + X)
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8 0
2 years ago
Hydrazine, N2H4, may react with oxygen to form nitrogen gas and water.
Sindrei [870]

Answer:

The percent yield of the reaction is 35 %

Explanation:

In the reaction, 1 mol of hydrazine reacts with 1 mol O₂ to produce 1 mol of nitrogen and 2 moles of water.

Let's verify the moles that were used in the reaction.

2.05 g . 1mol/ 32 g = 0.0640 mol

In the 100% yield, 1 mol of hydrazine produce 1 mol of N₂ so If I used 0.0640 moles of reactant, I made 0.0640 moles of products.

Let's use the Ideal Gases Law equation to find out the real moles of nitrogen, I made (real yield).

1atm . 0.550L = n . 0.082 . 295K

(1atm . 0.550L) / 0.082 . 295K = n → 0.0225 moles

Percent yield of reaction = (Real yield / Theoretical yield) . 100

(0.0225 / 0.0640) . 100 = 35%

3 0
2 years ago
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What is meant by the negative sign in an answer like"-46.8kJ"? When would you use a positive sign
MA_775_DIABLO [31]
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3 years ago
The equations given in the problem introduction can be added together to give the following reaction: overall: N2O4→2NO2 However
Murljashka [212]

Answer:

Reverse the 2 NO_2 \longrightarrow 2 NO + O_2  reaction

Explanation:

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N_2O_4 \longrightarrow 2 NO + O_2

Overall:

N_2O_4 \longrightarrow 2 NO_2

As can be seen, in the overall reaction we have N_2O_4 in the reactants like in the second reaction and NO_2 in the products. The NO_2 is in the first reaction but as a reactant so we need to reverse that reaction:

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N_2O_4 \longrightarrow 2 NO + O_2

Combining:

N_2O_4 + 2 NO + O_2\longrightarrow 2 NO + O_2 + 2 NO_2

N_2O_4 \longrightarrow 2 NO_2

4 0
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