which of these changes are endothermic and which are exothermic

baking a cake
bending a plastic ruler
cutting paper
melting ice cream
ripening of fruit
souring of milk
​

If the earth is completely an oxidizing atmosphere, materials would ignite spontaneously when they are exposed to air.

Let us recall that oxidation has to do with an increase in oxidation number. If the earth is left as an oxidizing atmosphere without any attenuation, we can not have pure substances.

Secondly, materials would ignite spontaneously when they are exposed to the oxidizing atmosphere of the earth.

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The most common way to monitor the rate of reaction is by observing the increase in the absorbance of the solution.

The rate of reaction is the rate at which reactants are converted into products or the rate at which the reactants disappear.

Given that the reaction is a colorimetric reaction, the most common way to monitor the rate of reaction is by observing the increase in the absorbance of the solution.

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Answer:

n

Explanation:

nobody knows

The temperature of 0.049 moles of a Ne with a pressure of 1.00 atm and a volume of 2.50 L is 621.44K.

The temperature of a given gas can be calculated using the ideal gas law equation:

PV = nRT

Where;

P = pressure = 1.00 atm

V = volume =2.50 L

R = gas law constant = 0.0821 Latm/molK

Mass =1.00 gram

The molar mass of Ne= 20.1797 u

[tex]Moles = \frac{mass}{molar \;mass}[/tex]

[tex]Moles = \frac{1.00}{20.1797}[/tex]

Moles = 0.049mol

T = temperature=?

Putting the value in the equation:

PV = nRT

1.00 atm × 2.50 L = 0.049mol × 0.0821 × T

T = 621.44K

Therefore, the temperature of 0.049 moles of a Ne with a pressure of 1.00 atm and a volume of 2.50 L is 621.44K.

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Answer:

0.893mol

Explanation:

n = m ÷ M

= 275 ÷ (23 + 80)

= 2.67 mol

* now use the Mol ratio *

NaBr : FeBr3

6 : 2

2.67 : x

5.67 = 6x

n( FeBr3 ) = 0.893 mol

Answer:

The percentage composition of a given compound is defined as the ratio of the amount of each element to the total amount of individual elements present in the compound multiplied by 100. Here, the quantity is measured in terms of grams of the elements present.

please give me brainliest

Answer:

B. the reaction absorbs energy (+ or endothermiic)

The weakness of the rutherford model of the atom that bohr addressed is that

The Rutherford model of the atom proposed by Ernest Rutherford in 1911 shows that the atom is much hollow space with its mass concentrated at the center being surrounded by electrons. It is the planetary model.

The Bohr model of the atom proposed by Neils Bohr in 1913 suggests that

The weakness of the rutherford model of the atom that bohr addressed is that

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Answer:

False

Explanation:

Because laws and theories are developed for different purposes, laws never become theories, and theories do not become laws.

Mass of hydrate + crucible = 47.29 g

Mass of anhydrous salt = 2.7 g

Molar mass of anhydrous salt CuSO4 = 159.5 g

Given,

mass of empty crucible = 42.45 g

mass of hydrate salt= 4.84 g

mass of crucible after first heating = 46.1 g

mass of crucible after second heating= 45.153 g

mass of crucible after third heating= 45.15 g

so, as per the question we need to find...

Mass of hydrate + crucible = ? g

Mass of anhydrous salt = ? g

Molar mass of anhydrous salt CuSO4 = ? g

∴Mass of hydrate + crucible = 42.45 + 4.48 = 47.29 g

The given salt is in hydrate form, to remove water from this molecule we need to perform heating .

So we are taking the substance into the crucible as it is in less quantity.

Here, we performed heating 3 times and note the weight after every heating.

After this, assume that the water is totally evaporated and the remaining salt is in anhydrous form,

∴ Mass of anhydrous salt = 45.15 - 42.45 = 2.7 g

To find the molar mass of anhydrous salt of CuSO4,

atomic weight of Cu = 63.5 g

atomic weight of S = 32 g

atomic weight of O =16 g

∴ molar mass of anhydrous salt of CuSO4 = 63.5 + 32 + (16 ×3)

                                                                   =159.5 gm

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Answer:

Electric current

Definition:

The time rate of flow of electric charge, in the direction that a positive moving charge would take and having magnitude equal to the quantity of charge per unit time: measured in amperes.

Everything begins inside in the battery. The battery's zinc metal undergoes oxidation; here is where the flow of electrons into the conductors begins. Electrical field attraction will lead the wire's existing electrons to move towards the battery's positive terminal, and the loose electrons caused by the zinc metal will begin to fill the wire's empty spaces. process continues until the zinc metal's oxidation ceases. At rechargeable batteries, the oxidation-reduction process is also reversed by charging the battery, allowing the stored electrons in the positive terminal to flow back to the zinc metal's negative terminal.

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Answer:

C.) 4.85 x 10⁻¹⁹ J

Explanation:

To find the energy, you need to use the following equation:

E = hc / w

In this formula,

-----> E = energy (J)

-----> h = Planck's Constant (6.626 x 10⁻³⁴ J*s)

-----> c = speed of light (3.00 x 10⁸ m/s)

-----> w = wavelength (m)

Once you have converted nanometers to meters, you can plug the given values into the equation and solve.

410 nm                1 m
-------------  x  ----------------------  =  4.10 x 10⁻⁷ m
                        1 x 10⁹ nm

E = hc / w

E = (6.626 x 10⁻³⁴ J*s)(3.00 x 10⁸ m/s) / (4.10 x 10⁻⁷ m)

E = 4.85 x 10⁻¹⁹ J

+3

Hence, the magnetic behaviour of the complex is paramagnetic. The oxidation number of the central metal atom: The oxidation number of the metal iron is +3.

Answer:

the oxidation number of iron in the complexion is +3 or x=+3

The alkaline earth metals are also referred to as Group 2A. elements are comparable to one another in terms of their electron configurations and thus, their properties.

From beryllium (Be) through radium, the alkaline-earth metals comprise Group 2 of the periodic table (Ra). The alkaline earth metals are so reactive because each of these elements has two electrons in its lowest energy level that they are rarely encountered alone in nature. However, they don't react as quickly as alkali metals do. Compared to the alkali metals, their chemical reactions normally proceed more slowly and generate less heat.

Be :- [He]2S2

Mg:-[Ne]3S2

Ca :-[Ar]4S2

Sr:-[Kr]5S2

Ba:-[Xe]6S2

Ra:-[Rn]7S2

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Group 2A is another name for the alkaline earth metals, which are similar to one another in terms of their electron configurations and thus, their properties.

Group 2 of the periodic table is made up of alkaline-earth metals, starting with beryllium (Be) and ending with radium (Ra). The fact that each of these elements possesses two electrons at its lowest energy level makes the alkaline earth metals extremely reactive, which is why they are rarely found by themselves in nature. They don't respond as quickly, though, as alkali metals do. Their chemical reactions often take longer and produce less heat than those of the alkali metals.

Be:- [He]2S2

Mg:-[Ne]3S2

Ca:-[Ar]4S2

Sr:-[Kr]5S2

Ba:-[Xe]6S2

Ra:-[Rn]7S2

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Answer:

b

Explanation:

b is the ketone because it is and that's a fact

Answer:

D

Explanation:

Ketones are a class of organic compounds that have an Oxygen double bonded to the middle of the main carbon chain.

Option A is not a ketone (despite having an Oxygen double bonded to the middle of the main carbon chain) because it has an adjacent single bonded Oxygen in the main carbon chain.  This type of compound is classified as an "Ester".

Option B is not a ketone, but is instead classified as an aldehyde, a group of compounds with their Oxygen double bonded at the end of the main carbon chain.

Option C is not a ketone (despite having an Oxygen double bonded to the middle of the main carbon chain), but is instead classified as an Carboxylic Acid, because it has an adjacent single bonded Oxygen in the main carbon chain, and both of these pieces (with the single bonded O pointing outward) are at the end of the main carbon chain.

Option D is a ketone because it does have an Oxygen double bonded somewhere to the middle of main carbon chain, not at an end, and not with another Oxygen single bonded adjacently in the carbon chain.  Specifically, this ketone is "2-pentanone" or "methyl propyl ketone"

Answer:

Calcite

Explanation:

When in contact with hydrochloric acid, calcite releases carbon dioxide gas.

24.25 moles of NO can be produced using 97 moles of HNO3.

Equal numbers of atoms from various elements are present in both the reactants and the products in balanced chemical equations. Varied elements' atom counts in the reactants and products of unbalanced chemical equations are different.

3 Cu + 8HNO3 g → 3 Cu(NO3)2 + 2 NO + 4 H2O

The number of moles consumed can be calculated using comparing with coefficients in the balanced reaction .

So , from above eq we get that 8 moles of HNO3 are consumed to make 2 moles of NO.

⇒  8 HNO3⇔2 NO

⇒ 1 HNO3⇔ 1/4 NO

This means that for each mole of HNO3 produces 1/4 moles of NO.

So , for 97 moles of HNO3 , [tex]\frac{1}{4} *97[/tex] moles of NO can be made,

So, total moles of NO made are 24.25 moles.

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24.25 moles of NO would be made when 97 moles of [tex]HNO_{3}[/tex] are consumed

Given reaction:

[tex]3 Cu + 8HNO_{3} - > 3 Cu(NO_{3})_{2} + 2 NO + 4 H_{2}O[/tex]

As the given reaction is already balanced so we don't need to balance it

In a balanced chemical reaction the ratio of reactants consumed and products formed always remains constant.

∵ In the given Reaction we can analyse for 8 moles [tex]HNO_{3}[/tex] consumed 2 moles of [tex]NO[/tex] are being produced.

Assuming [tex]x[/tex] moles of [tex]NO[/tex] being produced when [tex]97[/tex] moles [tex]HNO_{3[/tex] produced

∵ Ratio remains constant

⇒[tex]\frac{HNO_{3} Consumed}{NO Produced} = \frac{8}{2} =\frac{97}{x}[/tex]

⇒[tex]x=\frac{97}{4}=24.25[/tex] moles

∴ 24.25 moles of [tex]NO[/tex] would be made.

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The label appears in the organic product and not in the water owing to the fact that water is eliminated as -OCH3 replaces -OH.

Isotopic labelling is one of the methods by which a chemical reaction is studied. In this case, we can see that the reaction occurs with the hemiacetal reacting with a labeled methanol.

By looking at the reaction products we can see that the label appears in the organic product and not in the water owing to the fact that water is eliminated as -OCH3 replaces -OH.

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Answer:

9.519e^-2

Explanation:

To accurately show the number in scientific notation, you need to move the decimal place to the left 2 spaces. Because you are moving the decimal place to the left, the exponent will be a negative number. Because the decimal place moves 2 units to the left, the exponent will be a -2.

Therefore, the answer in correct scientific notation is:

951.9 ----------> 9.519e^-2

Answer:

chemical because it turned into a new compound

Explanation:

is zinc and hydrogen chloride combining into zinc chloride and hydrogen gas a chemical or physical change?​

physical change is like  boiling, melting, freezing, and shredding

but its still the same compound

chemical is like it turns into something else like a new compound

Zn + 2HCl = ZnCl2 + H2(g)

Metal + Acid → Hydrogen + Acid Anion

new compound forms in this reaction

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Answer: C

Explanation:

iron sulfide.

Answer:

C. Iron sulfide

Explanation:

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This happens because the beaker is open.

The Law of Mass Conservation says that in a close system all the mass and energy should be the same.

If the system is open, as in the case, we can have loss of mass, due to formation of gas, that will leave the beaker to the environment, and we can also have loss of energy, because the system will exchange the energy, as heat, with the environment, causing a loss on the total energy.

Answer:

Its C its C its C

Explanation:

i dislike expert verifeid beacause he wont say C

Answer:

Tin bromine = Snbr2

aluminum fluorate = AlFe3

iron oxide = Fe2o3

potassium chloride = KCL or 2KCL = K2CL2

All Pairs are correct

The gas given off at the cathode is hydrogen while the gas given off at the anode is oxygen.

The term electrolysis has to do with the decomposition of a substance by the passage of a direct current through it.

The ions present in the system are[tex]H^+[/tex], [tex]OH^-[/tex] and [tex]NO_3^-[/tex] ions. The gas given off at the cathode is hydrogen while the gas given off at the anode is oxygen.

The half-reaction equation of the reduction is;

[tex]2H^+(aq) + e[/tex] → [tex]H_2(g)[/tex]

The oxidation half-reaction equation is;

[tex]4OH^- (aq)[/tex] → [tex]2H_2O(l) + 4e[/tex]

The overall equation is;

[tex]4H^+(aq) + 4OH^- (aq)[/tex] → [tex]4H_2(g) + 2H_2O(l) + 4e[/tex]

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Answer:

B

Explanation:

The answer is B, O2

O₂ is the limiting reagent.

A limiting reactant is described as the one that will be consumed first in a chemical reaction.

C₁₀H₈ + 12O₂ → 10CO₂ + 4H₂O

Given, Mass of O₂ = 23.3 g

           Mass of C₁₀H₈ = 18.3 g

Molar mass of O₂ = 32 g

No. of moles of O₂ = 32/23.3 = 1.4 moles

Molar mass of C₁₀H₈ = 128 g

No. of moles of C₁₀H₈ = 128/18.3 = 6.9 = 7 moles

According to the equation,

1 mole of C₁₀H₈ yields 10 moles of CO₂. So, 7 moles of C₁₀H₈, give 70 moles of CO₂.

12 moles of O₂ yields 10 moles of CO₂. So, 1.4 moles of O₂ give 1.16 moles of CO₂.

We do know, however, that based on our balanced equation, if we were to totally react all 1.4 moles of O2, we could only produce a maximum of 1.16 moles of CO2. Even while there is enough C10H8 to generate more, the amount of O2 we have is a limiting factor because it will be consumed first.

So, our limiting reactant is O₂.

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Answer: a. hydrogen

This is a fact.

Carbon is the reference taken to assign the atomic mass unit

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Answer: Initially when the student spilled the bottle of ammonia the ammonia gas particles diffused with the particles of air in the room. We know that the rate of diffusion of gases is very high. So the entire room filled up with the pungent smell of ammonia.

When he opened the doors and windows and switched on the exhaust fan, the air from the room along with the ammonia gas diffused with the air outside the room.Moreover, outside air entered into the room so the concentration of ammonia gas in the room air reduced.Due to these reasons the student got relief.

Answer:

CO_(2)` molecules removed `= 10^(21)` <br> No. of `CO_(2)` molecules left `= 2.74 xx 10^(21) - 10^(21) = 1.74 xx10^(21)` <br>

Explanation: