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lorasvet [3.4K]
3 years ago
6

Which two changes can indicate that a physical change has occurred in a substance?

Chemistry
2 answers:
tester [92]3 years ago
6 0
I think the answer would be B and C but sorry if it’s wrong
inn [45]3 years ago
5 0
I believe it's b!! good luck! sorry if it's wrong
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Both diamond and graphite (i.e. pencil lead) consist of carbon atoms. They are only different in their crystalline structures. O
prisoha [69]

Answer:

Moles of carbon atoms  = 3.33  ×  10^{-6} mol

No. of atoms of C in Diamond  = 2.007 ×   10^{28} atom

Atoms of graphite = 6.27 × 10^{23} Atoms

Explanation:

given data

Cost of 0.2g of diamond = $5000

Cost of 25 g of graphite = $ 2

solution

we know cost of 0.2g of diamond is $ 5000 so that for 1$

if buy 1$ = \frac{0.20}{5000}

1$ = 4.0 × 10^{-5} g Carbon

and Moles of carbon atoms  is express as

Moles of carbon atoms = Given mass of Carbon ÷ atomic mass of C      .........1

Moles of carbon atoms  = 4.0  ×  10^{-5}    g/ 2.0g

Moles of carbon atoms  = 3.33  ×  10^{-6} mol

and

No. of atoms of C in Diamond = No. of moles × Avogadro NO    ..............2

No. of atoms of C in Diamond  = 3.33 ×   10^{-6} mol × 6.022 ×   10^{28}

No. of atoms of C in Diamond  = 2.007 ×   10^{28} atom

Graphite

and wew have given Cost of 25 g of graphite is $2 so for but 1$ we get

for buy $1 = 25÷2  = 12.5 g Of graphite

Moles of graphite = 12.5÷12 = 1.04 mol

Atoms of graphite = 1.04 × 6.022 × 1023

Atoms of graphite = 6.27 × 10^{23} Atoms

6 0
3 years ago
Identify which do not belong to the group?
nevsk [136]

Answer:

bronchi

epiglottis

plasma

Mittal

alveoli

5 0
3 years ago
Read 2 more answers
If the products of a reaction are Co2 and 2H20, what is known about the<br>reactants?​
Svetradugi [14.3K]

Answer:

Reactant : A combustion of hydrocarbon.

Explanation:

It is known that when hydrocarbons are involved in combustion, they produce carbon dioxide and water.

CxHy + (x+y/4)O2 ===> xCO2 + y/2H2O

4 0
3 years ago
Help idk if I got the right answer <br><br> A<br><br> D<br><br> B<br><br> C<br><br> E
olganol [36]

Answer:

b

Explanation:

3 0
4 years ago
Water has the following thermodynamic values: ΔH°fus of H2O = 6.02 kJ/mol ΔH°vap of H2O = 40.7 kJ/mol heat capacity of solid H2O
Brrunno [24]

Answer:

Qtotal = 90.004 kJ

Explanation:

To start resolving the problem we need to first convert the kJ/mol units from the thermodynamic values to J/g, so that we can work with the units of the heat capacity values. We know that the molar mass of water is 18.015 g/mol, so with this we do the respective conversion:

ΔH°fus of H2O = (6.02 kJ/mol) (1 mol/18.015g) (1000J/kJ) = 334.165 J/g

ΔH°vap of H2O = (40.7 kJ/mol) (1mol/18.015g) (1000J/kJ) = 2259.228 J/g

Now we need to find out the heat energy required to rise the temperature (specific heat capacity) and the energy required for each change of phase (specific latent heat), and add everything up. For this we will require the specific heat capacity and latent heat equations:

Q = mCΔT ; where m = mass, C = Hear capacity, ΔT = change of temperature

Q = mL ; where m = mass, L = specific latent heat

<u />

<u>First change of phase (solid to liquid - fusion)</u>

Q1 = (25g) (2.09 J/g°C) (0°C - (-129°C) = 6740.25 J

Q2 = (25g) (334.165 J/g) = 8354.125 J

<u>Second change of phase (liquid to gas - vaporization)</u>

Q3 = (25g) (4.18 J/g°C) (100°C - 0°C = 10450 J

Q4 = (25g) (2259.228 J/g) = 56480.7 J

<u>Rise of temperature of the gaseous water</u>

Q5 = (25g) (1.97 J/g°C) (262°C - 100°C = 7978.5 J

Finally we add everything up:

Qtotal = Q1 + Q2 + Q3 + Q4 + Q5 = 6740.25 J + 8354.125 J + 10450 J + 56480.7 J + 7978.5 J = 90003.575 J = 90.004 kJ

8 0
3 years ago
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