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KonstantinChe [14]
3 years ago
5

Which of these are physical changes in matter chech all that apply

Chemistry
2 answers:
Bogdan [553]3 years ago
8 0

Explanation:

Changes that are unable to bring any difference in chemical composition of a substance are known as physical change.

For example, change in shape, size, mass, volume, density, boiling or freezing point etc are all physical changes.

Whereas changes that bring difference in chemical composition of a substance are known as chemical changes.

For example, reactivity, toxicity, combustion etc are all chemical changes.

Hence, out of the given options physical changes are classified as follows.

  • Boiling water
  • A pencil being sharpened
  • Freezing water

serious [3.7K]3 years ago
6 0

Answer:

a pencil being sharpened

freezing water

boiling water

Explanation:

a physical change doesn't change the chemical structure of an object. That is why the other 2 are wrong

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What is the percent yield of LiCl if I produced 30.85g LiCl and my theoretical yield was calculated to be 35.40g LiCl?
marissa [1.9K]

Answer:

87.15%

Explanation:

To find percent yield, we can use this simple equation

\frac{Actual}{Theoretical} *100

Where "Actual" is the amount in grams actually collected from the reaction, and "Theoretical" is, well, the theoretical amount that should have been produced.

They give us these values, so to find the percent yield, just plug the numbers in.

\frac{30.85}{35.40} *100\\\\ =87.15

So, the percent yield is 87.15%

An easy trick to remember how to do this is just to divide the smaller number by the bigger number and move the decimal back two places. If you have a percent yield greater than 100%, something is wrong in the reaction.

7 0
3 years ago
The standard free energy of activation of one reaction A is 95.00 kJ mol–1 (22.71 kcal mol–1). The standard free energy of activ
diamong [38]

Answer:

The answer to the questions are as follows

Reaction B is 4426.28 times faster than reaction A

(b) Reaction B is faster.

Explanation:

To solve the question we are meant to compare both reactions to see which one is faster

The values of the given activation energies are as follows

For A

Ea = 95.00 kJ mol–1 (22.71 kcal mol–1) and

for  B

Ea = 74.20 kJ mol–1 (17.73 kcal mol–1)

T is the same for both reactions and is equal to 298 k

Concentration of both reaction = 1M

The Arrhenius Law is given by

k = Ae^{\frac{-E_{a} }{RT} }

Where

k = rate constant

Ea = activation energy

R = universal gas constant

T = temperature  (Kelvin )

A = Arrhenius factor

Therefore

For reaction A, the rate constant k₁ is given by k₁ = Ae^{\frac{-95000}{(8.314)(298)} }

And for B the rate constant k₂ is given by k₂ = Ae^{\frac{-74200 }{(8.314)(298)} }

k₁ = A×2.225×10⁻¹⁷

k₂ = A×9.850×10⁻¹⁴

As seen from the above Reaction B is faster than reaction A by (A×9.850×10⁻¹⁴)/(A×2.225×10⁻¹⁷) or 4426.28 times

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3 years ago
How is a hydrogen-1 atom different form a hydrogen-2 atom? How are they similar?
alina1380 [7]
If you’re referring to H vs H2,

H is usually found in ion form as H+

H2 is the designation for pure hydrogen gas, as it is diatomic and can only exist on its own in nature if it’s bonded to another H atom.

In this case, H is an ion and H2 is hydrogen gas

The way you wrote them out, though, indicates that they could be something different. Maybe isotopes? In this case the 1 and 2 are indicative of the amount of neutrons that the atom has.
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4 years ago
Uranium and radium are found in many rocky soils throughout the world. Both undergo radioactive decay, and one of the products i
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(a) <u>0.15 Bq/L</u> is the safe level of radon in Bq/L of air/

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Radionuclides are radioactive isotopes or unstable forms of elements.  Radioactivity is the release of energy, radiation, that occurs when these unstable elements decay or breakdown into more stable elements.  This process is known as radioactive decay and is measured by the half-life of the element.  The half-life is the time required for half of the original element to decay.  The half-life for radionuclides can range from a few thousands of a second to a few billion years.

The two most common radionuclides found in groundwater supplies are Uranium and Radium.  Uranium and Radium are naturally occurring elements that are found throughout the Mid-Atlantic and Northeastern United States in bedrock deposits like shale or granite deep below the surface.  Rather than the glowing green rocks often portrayed in cinema or television, uranium and radium are found in ores mixed with other minerals and metals.  

Uranium is the largest naturally occurring element on earth, nearly 70% denser than lead, and exists naturally as three different isotopes: U-234, U-235, and U-238, with U-238 and U-235 being the most common.  U-235 is the preferred isotope for nuclear power generation.  All three forms of uranium have the same chemical and physical properties, but have different radioactive properties.

In very low pH conditions, uranium exists in a cation oxidized form UO2, but it is most commonly present as anionic compounds UO2(CO3)2 and UO2(CO3)3.  As uranium decays naturally over time, it releases radiation and forms new elements like radium, lead, and radon gas.

Learn more about radon

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5 0
1 year ago
What elements are in the Same period as chlorine
Y_Kistochka [10]

Answer:   sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon.

Explanation:

8 0
3 years ago
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