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masha68 [24]
3 years ago
8

A chemistry teacher carried out several demonstrations, and students recorded their observations. For one of the demonstrations,

a student concluded that a physical change took place, but not a chemical change. Which of the following observations could the student have made of the results of the demonstration?
Chemistry
2 answers:
PIT_PIT [208]3 years ago
4 0

Answer:

It demonstrates that it a physical change because you can't see nothing happening but something happening

Sry if it doesn't make sense

taurus [48]3 years ago
3 0

The given question is incomplete. The complete question is:

A chemistry teacher carried out several demonstrations, and students recorded their observations. For one of the demonstrations, a student concluded that a physical change took place, but not a chemical change. Which of the following observations could the student have made of the results of the demonstration?

a) Two colorless solutions were combined, and the resulting solution was pink.

b)  When a solid was added to a liquid, sparks were produced.

c) One piece of solid substance was changed into small pieces.

d) When two solutions were combined, a precipitate formed.

Answer: One piece of solid substance was changed into small pieces.

Explanation:

Physical change is defined as the change in which shape and size of a substance changes, There is no change in the composition of the substance as no new substance is forming. It is usually an reversible reaction.

Chemical change is defined as the change in which a change is the chemical composition takes place resulting in the formation of new substance. It is usually an irreversible reaction.

Indicators showing chemical changes are :

Color change

Characteristic odor

Formation of bubbles

Formation of precipitate

Thus the given change is a physical change as only the physical state i.e. size of solid substance was changed into small pieces.

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Chlorine has two naturally stable isotopes: 35Cl (34.968853 amu) and 37Cl (36.965903 amu). The natural abundance of each isotope
allochka39001 [22]

Answer:

35Cl ⇒ 34.968853 amu  has an abundance of 30.05%

Explanation:

The molar mass of chlorine, (which is the average of all its naturally stable isotope masses), is 36.36575 amu.

There are 2 naturally stable isotopes, this means together they have an abundance of 100%

The isotopes are:

35Cl ⇒ 34.968853 amu  has an abundance of X %

37Cl ⇒ 36.965903 amu  has an abundance of Y %

X + Y = 100%   OR X = 100% - Y

36.36575 = 34.968853X + 36.965903Y  

36.36575 = 34.968853(1-Y) + 36.936.96590365903Y

36.36575 = 34.968853 -34.968853Y + 36.965903Y

1.396897 = 1.99705Y

Y = 0.699 = 69.95%

X = 100-69.9 = 30.05%

To control, we can plug in the following equation:

34.968853 * 0.3005 + 36.965903 * 0.6995 = 36.3658

This means

37Cl ⇒ 36.965903 amu  has an abundance of 69.95 %

35Cl ⇒ 34.968853 amu  has an abundance of 30.05%

7 0
3 years ago
Which macromolecules break apart by hydrolysis?
ankoles [38]

Answer:

Dehydration synthesis reactions build molecules up and generally require energy, while hydrolysis reactions break molecules down and generally release energy. Carbohydrates, proteins, and nucleic acids are built up and broken down via these types of reactions, although the monomers involved are different in each case.

Explanation:

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You are given the drawing of 2 waves. Notice, wave A is taller and Wave B is thinner. Since wave A is taller, wave
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Wave "B" is thinner. Is this the whole question?
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Who was the scientist responsible for the theory of evolution by natural selection?
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Charles Darwin

Explanation:

Charles Darwin is more famous than his contemporary Alfred Russel Wallace who also developed the theory of evolution by natural selection. scientist who studies living organisms.J

8 0
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CH3OH can be synthesized by the following reaction.
puteri [66]

Answer:

A: There is 43.12 Liter of H2 needed

B: There is 21.56 liter of CO needed

Explanation:

Step 1: Data given

CO(g)+2H2(g)?CH3OH(g)

For 1 mol of CO consumed, we need 2 moles of H2 to produce 1 mol of CH3OH

Molar mass of CO = 28.01 g/mol

Molar mass of H2 = 2.02 g/mol

Molar mass of CH3OH = 32.04 g/mol

Step 2: What volume of H2 gas (in L), measured at 754mmHg and 90?C, is required to synthesize 23.0g CH3OH?

Pressure = 754 mmHg = 0.992 atm

Temperature = 90°C = 363 Kelvin

mass of CH3OH produced = 23.0 grams

Step 3: Calculate moles of CH3OH

Moles CH3OH = mass CH3OH / Molar mass CH3OH

Moles CH3OH = 23.0 grams / 32.04 g/mol

Moles CH3OH = 0.718 moles

Step 4: Calculate moles of H2

For 1 mol of CO consumed, we need 2 moles of H2 to produce 1 mol of CH3OH

For 0.718 moles CH3OH produced, we have 2*0.718 moles =1.436 moles of H2 and 0.718 moles of CO

Step 5: Calculate volume of H2

p*V = n*R*T

with p = the pressure = 0.992 atm

with V the volume = TO BE DETERMINED

with n = the number of moles = 1.436 moles H2

with R = the gasconstant = 0.08206 L*atm/ K*mol

with T = the temperature = 363 Kelvin

V = (n*R*T)/p

V = (1.436*0.08206*363)/0.992

V = 43.12 L

Step 6: Calculate volume of CO

p*V = n*R*T

with p = the pressure = 0.992 atm

with V the volume = TO BE DETERMINED

with n = the number of moles = 0.718  moles CO

with R = the gasconstant = 0.08206 L*atm/ K*mol

with T = the temperature = 363 Kelvin

V = (n*R*T)/p

V = (0.718*0.08206*363)/0.992

V = 21.56 L

A: There is 43.12 Liter of H2 needed

B: There is 21.56 liter of CO needed

3 0
3 years ago
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