is (H) a positive or negative value

Answers

Answer 1

Answer:

A chemical reaction that has a positive ΔH is said to be endothermic , while a chemical reaction that has a negative ΔH is said to be exothermic . What does it mean if the ΔH of a process is positive? It means that the system in which the chemical reaction is occurring is gaining energy.


Related Questions

A student was given a 2.850-g sample of a mixture of potassium nitrate and potassium bromide and was asked to find the percentage of each compound in the mixture. She dissolved the sample and added a solution that contained an excess of silver nitrate, AgNO3. The silver ion precipitated all of the bromide ion in the mixture as AgBr. It was filtered, dried, and weighed. Its mass was 1.740 g. What was the percentage of each compound in the mixture

Answers

Answer:

See explanation

Explanation:

The reaction occurs as follows;

KBr(aq) + AgNO3(aq) ----> AgBr(s) + KNO3(aq)

Number of moles of AgBr formed = mass /molar mass =1.740 g/187.77 g/mol = 0.0093 moles

From the reaction equation;

1 mole of KBr yields 1 mole of AgBr

Hence the number of moles of KBr reacted = 0.0093 moles

Mass of KBr present = 0.0093 moles × 119g/mol = 1.11 g

Mass of KNO3 = 2.850 g - 1.11 g = 1.74 g

Percentage of KBr = 1.11 g/2.850 g × 100 = 38.9%

Percentage of KNO3 = 1.74 g/2.850 g × 100 = 61.1%

PLEASE HELP ASAP

Barney was a very inventive scientist and tried to perform the same experiments as those by famous scientists from long ago. One of the most challenging experiments was to roll out a very thin film of gold and put X-ray film in a circle around it. The difficult part was to get ahold of some radioactivity that he could shoot at the thin film for gold. One day, he ran into The Great Gazoo and told him his goal. The Great Gazoo said he had the perfect substance for him that was radioactive and should work. The element was named after him and had the symbol Gz. Barney quickly went back to his lab to run the experiment. What Barney noticed is that all the radioactive particles went through the gold film and none of them ricocheted back, but all went straight through the gold. Being puzzled, he quickly went to the lab to analyze this unknown radioactive substance. He found that the atomic number was 119, the mass number was 305. After a few more tests, Barney realized what was wrong with Gz. Your task is to figure out what was wrong with Gz by answering the following questions:
Whose experiment was Barney trying to imitate?
Where would Gz be located on Earth’s periodic table, column and row?
Give as many details on Gz that you could predict based on its location on the periodic table: type of chemical (metal, metalloid, or nonmetal), reactivity, ionization energy, electronegativity, and size of element.
What would the elements electron configuration end in?
Why did all the radioactive particles go straight through the gold film?
What would the daughter product be for Gz? Give all details for the atomic number, mass number, number of protons, neutrons and electrons.
If Gz had worked correctly, like Barney intended, what type of decay should Gz have had?
If Gz had worked correctly, what would the daughter product be? Give all details for the atomic number, mass number, number of protons, neutrons and electrons.
If Gz had worked correctly, what element would it become?

Answers

Answer:

a) Barney wants to repeat the rutheford experiment

b) the element will be in row 8 column 1 being an alkali metal

c) it should be a radioactive element, with a lot of mass

Explanation:

n this exercise they indicate that the particle Gz has atomic number 119 and atomic mass 305 amu, when reviewing the element periodicity table with this atomic number it has not yet been discovered, it should be in row 8 column 1 therefore it should be an alkali metal .

Therefore, it has only one electron in its last orbit.

a) Barney wants to repeat the rutheford experiment

b) the element will be in row 8 column 1 being an alkali metal

c) it should be a radioactive element, with a lot of mass

How many moles of Cd and of N are contained in 132.4 g of Cd(N03)2-4H20? (b) How many molecules of water of hydration are in this same amount?

Answers

Answer: The given amount of [tex]Cd(NO_3)_2.4H_2O[/tex] contains 0.430 moles of Cd, 0.860 moles of N and [tex]2.59\times 10^{23}[/tex] molecules of water.

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)

Given mass of [tex]Cd(NO_3)_2.4H_2O[/tex] = 132.4 g

Molar mass of [tex]Cd(NO_3)_2.4H_2O[/tex] = 308.5 g/mol

Plugging values in equation 1:

[tex]\text{Moles of }Cd(NO_3)_2.4H_2O=\frac{132.4g}{308.5g/mol}=0.430 mol[/tex]

1 mole of [tex]Cd(NO_3)_2.4H_2O[/tex] contains 1 mole of Cd, 2 moles of nitrogen atom (N), 10 moles of oxygen atom (O) and 8 moles of hydrogen atom (H).

So, 0.430 moles of [tex]Cd(NO_3)_2.4H_2O[/tex] will contain = [tex](1\times 0.430) = 0.430mol[/tex] of Cd and [tex](2\times 0.430)=0.86mol[/tex] of N

According to the mole concept:

1 mole of a compound contains [tex]6.022\times 10^{23}[/tex] number of molecules

So, 0.430 moles of [tex]Cd(NO_3)_2.4H_2O[/tex] will contain = [tex]\frac{6.022\times 10^{23}}{1mol}\times 0.430mol=2.59\times 10^{23}[/tex] number of water molecules.

Hence, the given amount of [tex]Cd(NO_3)_2.4H_2O[/tex] contains 0.430 moles of Cd, 0.860 moles of N and [tex]2.59\times 10^{23}[/tex] molecules of water.

what is second explain it briefly​

Answers

Explanation:

it is that when an object is moving 25 m per sec to calculate its time we can simply divide 1.5 by 25 and multiply by 1

Which phrase correctly describes the molecular structure within a molecule?

Answers

Same molecular structure and same properties.

Molecular structure is three dimensional structure in which arrangement of atoms is placed.

The molecular structure of a compound determines the polarity and its reactivity.

The different states of matter solid, liquid and gas have different molecular structure and different properties from each other.

The molecular structure of a molecule will have same properties as of the entire molecule based on its state.

Learn more at https://brainly.com/question/24325752

Answer:

the location of atoms, groups, or ions relative to one another and the number, type, and location of covalent bonds

A compound was found to contain 90.6% lead (Pb) and 9.4% oxygen. What is the empirical formula for this compound?

Answers

Answer:

the answer is 47.9 and ik because I just had that question

The empirical formula of the compound is O₄Pb₃.

What is the empirical formula?

An Empirical system is the chemical system of a compound that offers the proportions of the elements gifted within the compound however not the real numbers or arrangement of atoms. This would be the lowest complete variety ratio of the elements within the compound.

Amount of lead (Pb) = 90.6%

⇒and amount of oxygen = 9.4%

taking the whole number ratio

o = 4

Pb = 3

∴ ⇒O: Pb=4:3

O4Pb3 answer.

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PLZ HELP ME A girl throws a ball and her dog chases it. What characteristic of living things is this dog demonstrating as it chases the ball?
A. Cells
B. Reproduction
C. Growth
D. Response ​

Answers

I'm not sure but I think its D.response

Predict the approximate Ksp of Cuz(AsO4)2 based on the measured potential of Cell 7. Use the equation given in the Background.

a. 1 x 10^-35

b. 4 x 10^14

c. 5 x 10^-17

d. 2 x 10^-21

Answers

Answer:

a. 1 x 10^-35

Explanation:

The correct compound given is: [tex]\mathsf{Cu_3(AsO_4)}_2[/tex]

To predict the approximate Ksp value of the given compound, we will need to express the oxidation-reduction half-reaction of the compound and its dissociation, then, we will use the Nernst equation to determine the approximate Ksp value.

To start with the reduction half-reaction:

[tex]\mathsf{Cu_3(AsO_4)_{2}(s) + 6e^- \to 2As O_{4}^{3-}_{(aq)}+3Cu(s) }[/tex]

The oxidation half-reaction is:

[tex]\mathsf{3Cu(s) \to 3CU^{2+}_{(aq)} + 6e^-}[/tex]

The overall cell reaction now is:

[tex]\mathsf{Cu_3(AsO_4)_{2}(s) \to 3Cu^+ (aq) + 2As O_{4}^{3-}_{(aq)} }[/tex]

From the reduction half-reduction, the number of moles of electrons (n) transferred is 6 moles.

By applying the Nernst equation:

[tex]\mathsf{E_{cell} = E^0_{cell} -\dfrac{0.0591V}{n}log [Cu^{2+}]^3[AsO_4^{3-}]^2 }[/tex]

At standard conditions;

The standard cell potential [tex]\mathsf{E^0_{cell} = -0.342 \ V}[/tex]

and [tex]\mathsf{E_{cell} = 0 \ V}[/tex] since it is at equilibrium.

[tex]\mathsf{0 = -0.342 -\dfrac{0.0591V}{6}log [Cu^{2+}]^3[AsO_4^{3-}]^2 } \\ \\ \\ \mathsf{0.342 = -\dfrac{0.0591V}{6}log [Cu^{2+}]^3[AsO_4^{3-}]^2 }[/tex]

[tex]\mathsf{log [Cu^{2+}]^3[AsO_4^{3-}]^2 = \dfrac{-(0.342)*6}{0.0591 }}[/tex]

[tex]\mathsf{log [Cu^{2+}]^3[AsO_4^{3-}]^2 = -34.7}[/tex]

[tex]\mathsf{log [Cu^{2+}]^3[AsO_4^{3-}]^2 \simeq -35}[/tex]

[tex]\mathsf{[Cu^{2+}]^3[AsO_4^{3-}]^2 = 10^{-35}}[/tex]

[tex]\mathbf{K_{sp} = [Cu^{2+}]^3[AsO_4^{3-}]^2 = 1\times 10^{-35}}[/tex]

What are 5 uses of nitrogen?

Answers

Answer:

nitrogen is used in the production of  1) fertilisers  2) nitric acid  3) nylon  4) dyes  and  5) explosives

please give me brainliest if you can :))

which is the answer?

Answers

Answer:

I could be wrong letter c

What is the answer to 9.7300x10^2+9.8700x 10^3 1.0843x 10^ in scientific notation

Answers

Explanation:

Your search - What is the answer to 9.7300x10^2+9.8700x 10^3 1.0843x 10^ in scientific notation - did not match any documents.

Suggestions:

Make sure that all words are spelled correctly.

Try different keywords.

Try more general keywords.

Try fewer keywords.

giúp tớ với, mình học lớp 9 ạ

Answers

Answer: broooo what is this

Explanation:

What will happen if we drink liquid nitrogen?

Answers

Because of its low temperature liquid nitrogen can be extremely damaging to body tissue, causing frostbite and cryogenic burning on contact. If ingested it can lead to severe internal damage, destroying tissue in the mouth and digestive tract.


Which of the following are held together by nonpolar covalent bonds?
The Periodic Table
A. Atoms of phosphorus (P) and chlorine (CI)
B. Atoms of chlorine (CI)
C. Atoms of chlorine (CI) and magnesium (Mg)
D. Atoms of magnesium (Mg)

Answers

Answer:

Answer: Atoms of chlorine (CI) and magnesium (Mg)

Answer: Atoms of chlorine (CI) and magnesium (Mg)is your answer

5+64
this is TOTALLY SOOOO hard so help me
^thats what she said

Answers

Answer:

69

Explanation:

I thought that I answer is correct

Answer:

The answer is 69

Explanation:

Because if you add one its 66, and so on, hope this helps! but if you add five it will be 69, if you need help with easy equations let me know

Hydrogen and oxygen combine in
the ratio of 1:8 by mass to form
water. What mass of oxygen gas
would be required to react
completely with 3 g of hydrogen
gas?

Answers

Answer:

hhshshhxujejushwhbwhsjs s hs

"Every action force creates a reaction force that is equal in strength and opposite in direction." This statement summarizes Newton's

Answers

Answer: Newton's Third Law of Motion.

Explanation:

Newton's Third Law of Motion simply states that every action force creates a reaction force and then, this reaction force will be equal in strength and opposite in direction.

The statement simply implies that in every interaction, there will be a pair of forces that is acting on the two interacting objects. An example of Newton's third law of motion can be seen when a person jumps, thenlegs of the person will apply a force to the ground which will then propel the person into the air.

I need help!!!! please

Answers

6.94 is much more closet to 7.016, so Li 7 is more abundant

what do y’all do when y’all brainly says “locked” and won’t show anymore answers !???

Answers

Answer:

Create a new account as the thing you're experiencing now is due to the fact that Brainly had blocked your account.

hii pls help me to balance the equation and state the symbols thanksss​

Answers

Ca(s)+ H2O (l)----->H2 +Ca(oH)2

Ca(s)+2H2O(l)----->H2(g)+Ca(oH)2

I hope this helps

sorry if it's wrong

What is the AHsol for LiF → Lit + F-? The lattice energy is -1,036 kJ/
mol, the enthalpy of hydration for Lit is -499
kJ/mol, and the enthalpy of hydration for F-is-431 kJ/mol. Use A Hooi = -A Hat + AHhydr.
0-968 kJ/mol
-106 kJ/mol
106 kJ/mol
1,966 kJ/
mol

Answers

The heat of hydration is defined as the heat absorbed or evolved when one mole of a substance undergoes hydration. The heat of solution is the enthalpy change associated with he dissolution of a solute. The lattice energy is the heat. Lattice energy is the energy released when the components of the lattice are brought together from infinity.

Hence the heat of solution for LiF → Li^+ + F- is -1966  kJ/mol

Given that;

Heat of hydration = ΔH solution – ΔH lattice energy

Where,

ΔH solution  = Heat of the solution

ΔH lattice energy = Lattice energy of the solution

The heat of solution or enthalpy of dissolution is defined as the enthalpy change associated with the dissolution of a solute in a solvent

From the formula above;

ΔH solution = Heat of hydration + ΔH lattice energy

Heat of hydration = [(-431) + (-499)] = -930 kJ/mol

ΔH solution = (-930) + (-1,036) = -1966  kJ/mol

Hence the heat of solution for LiF → Li^+ + F- is -1966  kJ/mol

https://brainly.com/question/13526282

two easy uses of mixture​

Answers

Explanation:

it helps to make juices.

It helps to make concentrated acid into dilute acid.

Answer:

Explanation:

Here are a few more examples:

1. Smoke and fog (Smog)

2. Dirt and water (Mud)

I forgot to add the answers i had to my question (While a balloon is being filled, if the temperature of the air in the balloon increases, what happens to it’s volume)
A) It stays the same
B) It deflates
C) It decreases
D) It increases

Answers

The correct answer is D ... and if the answer was added to the word "explode" .. it would have been more correct .

How many moles of oxygen are required to react completely with 5 mol C8H18?

Answers

Answer:

62.5 moles of O₂.

Explanation:

We'll begin by writing the balanced equation for the reaction. This is illustrated below:

2C₈H₁₈ + 25O₂ —> 16CO₂ + 18H₂O

From the balanced equation above,

2 moles of C₈H₁₈ reacted with 25 moles of O₂.

Finally, we shall determine the number of mole of O₂ needed to react with 5 moles of C₈H₁₈. This can be obtained as shown below:

From the balanced equation above,

2 moles of C₈H₁₈ reacted with 25 moles of O₂.

Therefore, 5 moles of C₈H₁₈ will react with = (5 × 25) / 2 = 62.5 moles of O₂.

Thus, 62.5 moles of O₂ is needed for the reaction.

9. During an experiment the students prepared three mixtures A)Starch in water B) Sodium chloride solution C) Tincture of Iodine. i) Students observed a visible beam of light through mixture A. Why? ii) Tincture of lodTe did not show Tyndall effect. Explain reason. ill) How can you relate particle size to Tyndall effect?​

Answers

Answer:

See explanation

Explanation:

Tyndall effect refers to the scattering of light in a solution. Tyndall effect occurs when the size of particles in the solution exceeds 1 nm in diameter. Such solutions are actually called false solutions.

In tincture of iodine, the size of particles in solution is less than 1 nm in diameter hence the solution does not exhibit Tyndall effect. Hence, tincture of iodine is a true solution.

Therefore, if the size of particles in solution exceeded 1nm in diameter, Tyndall effect is observed.

A piece of sodium metal can be described as?

Answers

it can be described as a pure metal

The gases in a hair spray can are at a temperature of 27oC and a pressure of 30 lbs/in2. If the
gases in the can reach a pressure of 90 lbs/in2, the can will explode. To what temperature must
the gases be raised in order for the can to explode? Assume constant volume. Show your work.

Answers

P1=30lb/in^2P2=90lb/in^2T1=27°CT2=?

Using Gay Lussac's Law

[tex]\boxed{\sf \dfrac{P_1}{T_1}=\dfrac{P_2}{T_2}}[/tex]

[tex]\\ \sf\longmapsto \dfrac{30}{27}=\dfrac{90}{T_1}[/tex]

[tex]\\ \sf\longmapsto T_1=\dfrac{90\times 27}{30}[/tex]

[tex]\\ \sf\longmapsto T_1=81°C[/tex]

Key Notes:-

Gay Lussac's Law:-

It states that at constant volume (V),The pressure(P) of fixed amount of gas caries directly with its absolute temperature(T).

[tex]\\ \sf\longmapsto P\propto T[/tex]

[tex]\\ \sf\longmapsto \dfrac{P}{T}=Constant[/tex]

[tex]\\ \sf\longmapsto \dfrac{P_1}{T_1}=\dfrac{P_2}{T_2}[/tex]

[tex]\\ \sf\longmapsto P_1T_2=P_2T_1[/tex]

The final temperature of the gases with 90 lbs/in² is equal to 627°C assuming the volume is constant.

What is Gay Lussac's law?

Gay-Lussac's law can be described as if the volume (V) of the gas remains constant then the pressure (P) is directly proportional to the absolute temperature (T) of the gas.

Gay Lussca's law in mathematical expression can be represented as:

P/T = k

It can be also represented as the pressure (P) being directly proportional to the temperature (T).

P ∝ T                            ( V of gas is constant)

or,    P₁/T₁ = P₂/T₂

Given, the initial temperature of the gas, T₁ = 27°C = 27 + 273 = 300 K

The initial pressure of the gas, P₁ = 30 lbs/in²

The final pressure of the gas,  P₂ = 90 lbs/in²

The final temperature of the gases in a hair spray can be determined as:

[tex]{\displaystyle \frac{P_1}{T_1} =\frac{P_2}{T_2}[/tex]

[tex]{\displaystyle T_2 =\frac{P_2\times T_1}{P_1}[/tex]

[tex]{\displaystyle T_2 =\frac{90\times 300}{30}[/tex]

T₂ = 900 K = 900 - 273

T₂ = 627°C

Learn more about Gay Lussac's law, here:

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A chemist sets up a chemical reaction but finds that none of the reactant molecules have the required activation energy. What is the result?

A.
Products will form with less energy input.
B.
No products will be formed.
C.
The products will form too quickly.
D.
Products will convert to reactants.

Answers

Answer:

B.

No products will be formed.

Define force and speed​

Answers

Force = The external energy that changes or tends to change the state of any body or object is called force.

Speed = The rate of distance is called speed.

Answer:

Force is a push or pull which changes or tend to change the position of a body.

The rate of change its position with time or magnitude is called speed.

what is the reactant(s) in the chemical equation below

3CO(g) + Fe2O3(s) 2Fe(s) + 3CO2(g)

Answers

Answer:

the reactants are carbon dioxide ,iron, oxygen

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