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

i need help with this asap..
1. What has shininess
2.ability to change its shape

Answers

I think it's metal if its abt science

Answer:

i think metal or glass not sure but i think its metal

Explanation:

Help me:) please and thanks! Part 3

Answers

Answer:

then this picture 11 Venkat and one person is

Explanation:

join date 20th December is not a problem with the topic of your name and address of the topic of your name and address of the topic of your name and address of the topic of your life in general is not available in the equation is the topic of your name and address

so nothing in this picture .

Ethanol (C2H5OH) reacts with oxygen gas in a combustion reaction. How many liters of carbon dioxide gas are produced at STP when 375 mL of a 75.0% ethanol solution by mass with a density of 1.22 g/mL reacts with excess oxygen?

Answers

The volume of carbon dioxide produced when 375 mL of a 75.0% ethanol solution by mass with a density of 1.22 g/mL reacts with excess oxygen is  667.52 L.

We are told in the question that the solution contains 75.0% ethanol solution by mass.

Hence;

Density of solution = mass/volume

mass = Density × volume = 1.22 g/mL × 375 mL = 457.5 g

Mass% = mass of solute/ mass of solution × 100

Mass of solute = x

Mass of solution = 457.5 g

Mass percent = 75.0%

Substituting values;

75 = x/457.5 + x × 100

75/100 = x/457.5 + x

0.75(457.5 + x) = x

343.125 + 0.75x = x

343.125  = x -  0.75x

x = 343.125/0.25

x = 1372.5 g

The equation of the reaction is;

C2H6O(l) + 3O2(g) → 2CO2(g) + 3H2O(l)

Number of moles of ethanol =  1372.5 g/46 g/mol = 29.8 moles

From the reaction equation;

2 moles of ethanol produces 2 moles of carbon dioxide

29.8 moles of ethanol also produces 29.8 moles of carbon dioxide

If 1 mole of carbon dioxide occupies 22.4 L

29.8 moles of carbon dioxide occupies 29.8 moles × 22.4 L/ 1 mole

= 667.52 L

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A solution is prepared by dissolving 15.0 g of table salt in 70.0g of water. Find(a) the mass percent of solute and (b) the mass percent of solvent. ​

Answers

Answer:

[(15g NaCl/(70+15)]*100 = % NaCl

{(70g H2O/(70+15)]*100 = % H2O

Explanation:

A solution is prepared by dissolving 15.0 g of table salt in 70.0g of water. (a) The mass percent of solute is 17.64 % and (b) The mass percent of solvent is 82.35 %.

How to calculate the Mass percent of solute ?

Mass percentage = [tex]\frac{\text{Mass of solute}}{\text{Mass of solute + Mass of solvent}}[/tex]  × 100

How to calculate the Mass percent of solvent ?

Mass percentage = [tex]\frac{\text{Mass of solvent}}{\text{Mass of solute + Mass of solvent}}[/tex] × 100

Here,

Mass of solute (table salt) = 15.0 g

Mass of solvent (water) = 70.0 g

(a) The mass percent of solute

Put the value in above formula we get

Mass percentage = [tex]\frac{\text{Mass of solute}}{\text{Mass of solute + Mass of solvent}}[/tex] × 100

                             = [tex]\frac{15}{15 + 70}[/tex] × 100

                             = [tex]\frac{15}{85}[/tex]  × 100

                             = 17.64 %

(b) The mass percent of solvent

Mass percentage = [tex]\frac{\text{Mass of solvent}}{\text{Mass of solute + Mass of solvent}}[/tex] × 100

                             = [tex]\frac{70}{15 + 70} \times 100[/tex]

                             = [tex]\frac{70}{85} \times 100[/tex]

                             = 82.35 %

Thus, we can say that (a) The mass percent of solute is 17.64 % and (b)  The mass percent of solvent is 82.35 %.

     

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What is the difference between a conductor and an insulator?

Answers

A conductor is what helps heat or electricity pass through an object. Examples of conductors are, silver, iron, aluminum, etc..

An insulator does the opposite and instead, stops either from going through. Examples of an insulator is paper, wood, rubber, etc.

The overall shape of a plant cell is most directly related to which of its parts?

Answers

Cell wall is the answer

Cell wall is a unique structure found in some organisms.

Answer: Cell wall

Explanation: Cell wall is a unique structure found only in some specific organisms like plants, bacteria, fungi etc. The cell wall in plants is predominantly made up of a polysaccharide called CELLULOSE. This carbohydrate confers upon the cell "rigidity".

The cell wall is an additive material including the cell membrane that coats the external part of the cell of plants, hence, it gives plant cells their characteristic shape. The cell wall contributes to the overall flexible but rigid shape of the plant cell, protecting the cell against physical or chemical stresses.

PLEASSE HELP gotta get the answers neowww, basically just match the letters with the things.

Answers

Answer:

North pole-A

South pole- F

Equator- E

Polar Easterlies-C

Prevailing Westerlies-D or B-not sure

Trade Winds-D or B-not sure

Jeremy left his bike outside overnight. When he woke up in the morning, there were water drops on the seat. When he went to ride his bike after lunch, he saw the water drops had disappeared. Which statement best describes what happened to the water?

A. The energy from the sun caused the water drops to condense.
B. The energy from the sun caused the water on the seat to boil.
C.The energy from the sun cooled the water, causing it to evaporate.
D.The energy from the sun heated the water, causing it to evaporate.

Answers

Answer:

D

Explanation:

a,b, and c wouldn't cause the reaction that Jermey expirenced


Does this aid in joining the two molecules?

Answers

Answer:

yes it does aid in joining the two molecules

Explanation:

Pls fast pls due today pls pls I don’t wanna fail

Answers

Answer:

2:true

3: true

4:false

5: true

Explanation:

explain the electrolysis of MgCl2 in aqueous solution

Answers

During electrolysis, a current is passed through the molten MgCl2, and when this happens, the Mg2+ ions move to the negative electrode where they PICK UP OR GAIN ELECTRONS. This is reduction. The Cl- ions move to the positive electrode where they LOSE ELECTRONS. This is oxidation.

Food waste, like a feather or a bone, fall into food, causing
contamination.
Physical
Chemical
Pest
Cross-conta

Answers

Answer:

what do I need to do?..

..

Feather or bone when fall into food causing Physical  contamination.

Food waste, like a feather or a bone etc fall into food causing Physical  contamination because the contaminants such as feather and bone are mixed in the food physically not chemically. These contaminants can be removed through physical means such as with the help of hand.

Some contaminants mix with the food chemically means they react with the food and produce something new. Such type of contaminants are present in liquid form so we can conclude that feather or a bone etc when fall into food causing Physical  contamination.

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How quickly the electron are moving through the circuit
A.Resistance
B.voltage
C.current

2.The strength with which electrons are pushed through the circuit?
A.Resistance
B.voltage
Current

Answers

Answer:

B

Explanation:

because the electrons are moving fast

B because electrons move very quickly

Pls help I will give u points pls

Answers

Answer:

i think D

Explanation:

Nylon is a synthetic material that has many uses. It is used in the production of machine parts, cookware, and fabric. Nylon is made from petroleum and natural gas. Suppose that there were a shortage of petroleum and natural gas. What would companies that produce nylon likely need to do? A. identify a different natural resource that nylon could be made from B. search for nylon in many different parts of the earth C. convert existing nylon back into petroleum and natural gas D. find a way to make nylon without using natural resources

Answers

In case of a shortage in petroleum and natural gas, a company should find a way to make nylon without using natural resources.

Nylon is a very important material used in numerous applications. As a result of this, the demand for nylon as a raw material has genuinely been on the high side ever since.

However, nylon production depends on petroleum and natural gas. It is possible that there could be a shortage of these resources since they are obtained from the environment. In such cases, a company should  find a way to make nylon without using natural resources.

Learn more about polymers: https://brainly.com/question/17555341

Answer:

identify a different natural resource that nylon could be made from

Explanation:

I just did this question

Cu(OH)₂ +H₃PO₄ = Cu₃(PO₄)₂+H₂O

how do i balance this equation

Answers

balanced equation =

3Cu(OH)2 + 2H3PO4 → Cu3(PO4)2 + 6H2O

What does the law of conservation of matter state?
a Matter can be created, destroyed, and changed.
b Matter can be destroyed and created, but not changed.
c Matter can be changed, but not created or destroyed.
d Matter can be created and changed, but not destroyed.​

Answers

The answer is c. Matter can be changed, but not created or destroyed.

an atom of chlorine has an amount number of 17 and a mass number of 37. how many protons neutrons, and electrons are in the atom?

Answers

Answer: There are 20 protons neutrons in the atom

In the first half of the citric acid cycle, ____________ is oxidized, yielding a pair of electrons that reduce a molecule of NAD to NADH.

Answers

Answer:

isocitrate

Explanation:

Identify the correct chemical name.
Select one:
a. calcium (II) hydroxide
b. chromium hydroxide
c. ammonium calcide
d. ammonium chloride​

Answers

The answer is D ammonium chloride
The answer is a because calcium is a substance

An aqueous solution has a volume of 2.0 L and contains 36.0g of glucose. If the Molar Mass of glucose is 180g/mol, what is the molarity of the solution
Convert grams of Glucose to moles of Glucose and then solve for Molarity
show all work.

Answers

Answer:

moles = 36/180 = 0.2 moles

molarity = 0.2/2 = 0.1 mol/dm3

The DEA has designated five chemicals often found in spice as _____ controlled substances, making it illegal to sell, buy, or possess these chemicals.

Answers

Answer:

I'm pretty sure this doesn't really connect with chemistry much but the answer should be Schedule 1 as stated by the Drug enforcement agency.

An elephant takes a deep breath, releasing 9.50g of CO2. How many molecules CO2 is this?

Answers

Answer:

3 significant figures.

Explanation:

So, a mole is essentially a group of things. In this case, a mole of carbon dioxide will contain

6.022 ⋅ 10 [ by the 23rd power]

molecules of carbon dioxide. In other words, in order to have

1 molecule  of carbon dioxide, you need to have 6.022 ⋅ 10 [by the 23rd power] molecules of carbon dioxide.

You know that 5.00 ⋅ 10 [ by the 2nd power]  molecules of carbon dioxide are exhaled from the lungs when we breathe out. You can use Avogadro's constant as a conversion factor to help you figure out how many molecules are present.

What makes solids, liquids, and gases different. Explain the hypothesis, prediction and experiments that can lead to scientific theory.

Answers

Answer: Gases, Liquids, and Solids

Gases

Explanation:

Behavior

gas liquid solid

assumes the shape and volume of its container

particles can move past one another assumes the shape of the part of the container which it occupies

particles can move/slide past one another retains a fixed volume and shape

rigid - particles locked into place

compressible

lots of free space between particles not easily compressible

little free space between particles not easily compressible

little free space between particles

flows easily

particles can move past one another flows easily

particles can move/slide past one another does not flow easily

rigid - particles cannot move/slide past one another

a hypothesis is a prediction based on a theory. If the Hypothesis comes true the theory is more accepted.

A scientific theory differs from a scientific fact or scientific law in that a theory explains "why" or "how": a fact is a simple, basic observation, whereas a law is a statement (often a mathematical equation) about a relationship between facts.

2KClO3 —> 2KCl2+ 3O2
true if balanced or false if not
reaction type 1: synthesis, 2: decomposition, 3: single replacement, 4: double replacement, 5: combustion

Answers

Answer:

False. The balanced equation should be

2KClO3-->2KCl + 3O2

it is a decomposition reaction.

The modern-day quantum model of the atom is better than John Dalton’s model because it
A. has set electron orbits.
B. has positive and negative particles in the nucleus.
C. can be represented in one dimension.
D. answers many questions about atoms.

Answers

Answer:

its D. answers many questions about atoms.

The modern-day quantum model of the atom is better than John Dalton’s model because it "  answers many questions about atoms."

What is quantum model ?

This concept also referred to as the quantum mechanical and wave mechanical model, would be the cornerstone of contemporary atomic theory. The fact that an electron inside an atom may only exist in a limited range of states or energy is analogous to a standing wave.

What is John Dalton’s model ?

Dalton proposed that the concept of atoms will be used to explain the laws of conservation of mass as well as definite proportions. Imagining atoms as "solid, massy, hard, impenetrable, moving objects," he claimed that almost all matter would be composed of these tiny, indivisible particles.

Dalton also stated that almost no atom might be formed, converted into another, as well as destroyed. The complex shapes of orbitals also known as electron clouds used in the quantum mechanical atomic model are areas of space where an electron is likely to be present. So rather than being based on certainty, this model would be probability based.

Therefore, the correct answer will be option (D)

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SEP Construct Explainations: Explain how a substance's flammability can indicate a chemical change.​

Answers

Answer:Wood for barbucue.

Explanation:

why does adding lemon juice to blueberry smoothie make it change colour from purple to pink

Answers

The stuff that is used to make lemon has a negative affect on the blueberry therefore the color will change
Because the white colour from lemon juice make the blueberry juice pink

Don’t understand this science Question.

Answers

What is the question?

Answer:

I got you..you need help but with which question?

Explanation:

Have a great day!

What type of chemical reaction is Al + FeO --> Al2O3 + Fe

Answers

Answer:

single reaction equation

Explanation:

Type of Chemical Reaction: For this reaction we have a single replacement reaction. Balancing Strategies: In this single replacement (also called displacement) reaction the Al and Fe are switching places.

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