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3 years ago

The atoms, molecules, or compounds present at the start of a chemical reaction that participate in the reaction.

Chemistry

2 answers:

morpeh [17]3 years ago

6 0

Answer:

For 1: The chemical species present at the start of the chemical reaction are reactants.

For 2: Hydrogen gas and oxygen gas synthesizing into liquid water is a chemical reaction.

Explanation:

For 1:

In a chemical equation, the chemical species are termed as reactants or products.

Reactants are defined as the species which react in the reaction and are written on the left side of the reaction arrow. They are present at the start of the reaction.

Products are defined as the species which are produced in the reaction and are written on the right side of the reaction arrow. They are present at the end of the reaction.

$\text{Reactants}\rightarrow \text{Products}$

Hence, the chemical species present at the start of the chemical reaction are reactants.

For 2:

Physical change is defined as the change in which change in shape and size takes place. The chemical composition of a substance remains the same. No new substance is formed during this.

Chemical change is defined as the change in which change in chemical composition takes place. A new substance is formed in this.

For the given options:

Option A: A solid chocolate is melting into liquid chocolate by providing heat. The shape of the chocolate is changing. So, its a physical change.

Option B: When a peanut shell is cracked up, the size of the peanut shell is changed. So, it is a physical change.

Option C: When water vapor is cooled down to form liquid water, no new substance is getting formed. So, it is a physical change.

Option D: When hydrogen gas reacts with oxygen gas, it leads to the formation of water. As, new substance is getting formed. So, it is a chemical change.

$2H_2+O_2\rightarrow 2H_2O$

Hence, hydrogen gas and oxygen gas synthesizing into liquid water is a chemical reaction.

Art [367]3 years ago

4 0

For the first one the answer is B. and the second one is D.

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Given that Δ H ∘ f [ Br ( g ) ] = 111.9 kJ ⋅ mol − 1 Δ H ∘ f [ C ( g ) ] = 716.7 kJ ⋅ mol − 1 Δ H ∘ f [ CBr 4 ( g ) ] = 29.4 kJ

JulsSmile [24]

Answer:

283.725 kJ ⋅ mol − 1

Explanation:

C(s) + 2Br2(g) ⇒ CBr4(g) , Δ H ∘ = 29.4 kJ ⋅ mol − 1

$\frac{1}{2}$ Br2(g) ⇒ Br(g) , Δ H ∘ = 111.9 kJ ⋅ mol − 1

C(s) ⇒ C(g) , Δ H ∘ = 716.7 kJ ⋅ mol − 1

4*eqn(2) + eqn(3) ⇒ 2Br2(g) + C(s) ⇒ 4 Br(g) + C(g) , Δ H ∘ = 1164.3 kJ ⋅ mol − 1

eqn(1) - eqn(4) ⇒ 4 Br(g) + C(g) ⇒ CBr4(g) , Δ H ∘ = -1134.9 kJ ⋅ mol − 1

so,

average bond enthalpy is $\frac{1134.9}{4}$ = 283.725 kJ ⋅ mol − 1

4 0

3 years ago

From the relative rates of effusion of ²³⁵UF₆ and ²³⁸UF₆ , find the number of steps needed to produce a sample of the enriched f

Dafna11 [192]

The number of steps required to manufacture a sample of the 3.0 mole% ²³⁵U enriched fuel used in many nuclear reactors from the relative rates of effusion of ²³⁵UF₆ and ²³⁸UF₆. ²³⁵U occurs naturally in an abundance of 0.72% are : mining, milling, conversion, enrichment, fuel fabrication and electricity generation.

<h3>What is Uranium abundance ? </h3>

The majority of the 500 commercial nuclear power reactors that are currently in operation or being built across the world need their fuel to be enriched in the U-235 isotope.
This enrichment is done commercially using centrifuges filled with gaseous uranium.
A laser-excitation-based method is being developed in Australia.
Uranium oxide needs to be changed into a fluoride before enrichment so that it can be treated as a gas at low temperature.
Uranium enrichment is a delicate technology from the perspective of non-proliferation and needs to be subject to strict international regulation. The capacity for world enrichment is vastly overbuilt.

The two isotopes of uranium that are most commonly found in nature are U-235 and U-238. The 'fission' or breaking of the U-235 atoms, which releases energy in the form of heat, is how nuclear reactors generate energy. The primary fissile isotope of uranium is U-235.

The U-235 isotope makes up 0.7% of naturally occurring uranium. The U-238 isotope, which has a small direct contribution to the fission process, makes up the majority of the remaining 99.3%. (though it does so indirectly by the formation of fissile isotopes of plutonium). A physical procedure called isotope separation is used to concentrate (or "enrich") one isotope in comparison to others. The majority of reactors are light water reactors (of the PWR and BWR kinds) and need their fuel to have uranium enriched by 0.7% to 3-5% U-235.

There is some interest in increasing the level of enrichment to around 7%, and even over 20% for particular special power reactor fuels, as high-assay LEU (HALEU).

Although uranium-235 and uranium-238 are chemically identical, they have different physical characteristics, most notably mass. The U-235 atom has an atomic mass of 235 units due to its 92 protons and 143 neutrons in its nucleus. The U-238 nucleus has 146 neutrons—three more than the U-235 nucleus—in addition to its 92 protons, giving it a mass of 238 units.

The isotopes may be separated due to the mass difference between U-235 and U-238, which also makes it possible to "enrich" or raise the proportion of U-235. This slight mass difference is used, directly or indirectly, in all current and historical enrichment procedures.

Some reactors employ naturally occurring uranium as its fuel, such as the British Magnox and Canadian Candu reactors. (By contrast, to manufacture at least 90% U-235, uranium needed for nuclear bombs would need to be enriched in facilities created just for that purpose.)

Uranium oxide from the mine is first transformed into uranium hexafluoride in a separate conversion plant because enrichment operations need the metal to be in a gaseous state at a low temperature.

To know more about Effusion please click here : brainly.com/question/22359712

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2 years ago

Dependent variable? ( what did we measore)?

lana66690 [7]

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3 years ago

What is the purpose of finding oxidation states in the half-reaction method for balancing equations?

vazorg [7]

Answer: