Which of the following involves a reaction in which energy is absorbed?
O A. An instant cold pack
O B. A car's engine
C. A chemical hand-warmer
O D. A campfire

Answers

Answer 1
A chemical hand warmer because you absorb the heat. Brainliest pls lol

Related Questions

number of balance electrons of a non ionized oxygen atom​

Answers

Do you mean valence electrons? I think it’s 7 I’m not sure though it’s been a while

Decide whether the element is a metal or nonmetal, if you can.


Element is a hard silvery-gray solid. Wires are fastened to each side of a 2 cm slab of it, and an ordinary household 9 V battery is hooked up so that it can feed electricity through the slab to an LED. But the LED stays dark

Answers

Answer:

The element is a nonmetal

Explanation:

Elements are broadly classified into metals and non metals. Metals conduct electricity while non metals do not conduct electricity.

If we look at this scenario described in the question, we can easily decipher that the element is a nonmetal because the LED stays dark. The LED should have been lit if electricity was passed through the element in question.

Hence, the element is a non metal.

5) The stability of an atom is determined by
Re 1) P+n
2)P-n
3) P/N
4) N/P

Answers

Answer:

the answer p+n

Explanation:

Please explain to me!!!

Answers

Answer:

nice handwrtting

Explanation:

18. What is one of the three things that cause the surface currents of the oceans?
A.differences in salinity
B.temperature differences
C. density differences
D. Coriolis effect

Answers

Answer:

b. temperature difference

There are four conditions an atom needs to meet to participate in hydrogen bonding. It needs to be_______ enough not to bump into other atoms when approaching the 1s orbital of the hydrogen, it needs to carry at least one________ atom, it needs to be_________enough to create a delta on the connected hydrogen, and it needs to have at least one________.

Answers

Answer:

The conditions are

1) Small enough

2) Electronegative atom

3) highly electronegative

4) lone pair of electrons

The correct statement therefore is

It needs to be small enough not to bump into other atoms when approaching the 1s orbital of the hydrogen, it needs to carry at least one electronegative atom, it needs to be highly electronegative enough to create a delta on the connected hydrogen, and it needs to have at least one lone pair of electrons.

Explanation:

Hydrogen bonding is a type of intermolecular bond that occurs between the partial positive charge (delta) on a hydrogen atom bonded to a small highly electronegative element (like nitrogen, oxygen or fluorine) and the free electrons on another electronegative element of another molecule.

The hydrogen atom with the partial positive charge (delta) is known as the hydrogen bond donor, while the electronegative element, carrying lone electrons is called the hydrogen bond acceptor.

Let's take a deeper look at these terms:

1) Hydrogen bond donor

Using water (H₂O) as an example, the high electronegativity of the oxygen atom covalently bonded to the hydrogen atom draws the lone electron in the 1s orbital of the hydrogen atom, creating a partial positive charge (d⁺) on the hydrogen atom. This is what happens within one water molecule

2) Hydrogen bond acceptor

When two or more molecules of water interact, the partial positive charge (d⁺) on the hydrogen atom of one molecule, is attracted to the valence or free electrons on the oxygen atom of a nearby molecule of water thus creating a dipole-dipole intermolecular bond known as a hydrogen bond.

             

For the hydrogen bond to be effective, the electronegative atom bonded to the hydrogen acting as the hydrogen bond donor in the first water molecule needs to be small enough so as not to disrupt the 1s orbital of the hydrogen atom. The smaller the size of the electronegative atom, the stronger the partial negative charge created on the hydrogen atom.

The valence or free pair of electrons on the electronegative (oxygen) atom of the second molecule of water (hydrogen bond acceptor) is what attracts the partial positive charge on the hydrogen atom to create the hydrogen bond

For the reaction 2Fe+o2 -->Feo how many grams of iron(ll) oxide are produced from 479.6 grams of iron in an excess of oxygen (Fe=56gmol, O=16g mol)

Answers

Mass of iron(ll) oxide= 616.608 g

Further explanation

Given

Reaction

2Fe+O2 -->2FeO

479.6 grams of iron

Required

mass of iron(ll) oxide

Solution

mol of iron :

= mass : Ar Fe

= 479.6 g : 56 g/mol

= 8.564

From the equation, mol FeO :

= 2/2 x mol Fe

= 2/2 x 8.564

= 8.564 moles

Mass of iron(ll) oxide :

= mol x MW

= 8.564 x 72 g/mol

= 616.608 g

please help. im freaking out rn. i have like 40 missing assignments please

Answers

Answer:

I'm pretty sure its the one that says very little at the beginning but if I get it wrong I'm sorry

Vitamin C is a covalent compound with the molecular
formula C6H8O6. The recommended daily dietary
allowance of vitamin C for children aged 4-8 years is
0.000142mol. What is the mass of this allowance in grams?

Answers

C3H403. obtained by diving by 2 to get simplest ratio

The mass allowance of Vitamin C for children aged 4-8 years is equal to 0.025 grams.

What is a mole?

A mole can be defined as a standard unit that can be utilized to evaluate the number of entities such as atoms, molecules, ions, or other particular particles in a particular amount of the substance.

The number of elementary entities present in one mole of any chemical substance was found to be equal to 6.023 × 10²³ which is also known as the Avogadro number.

Given, the number of moles of vitamin C = 0.000142 moles

Given, the molecular formula of Vitamin C is C₆H₈O₆.

The mass of one mole of C₆H₈O₆ = 176 g

One mole of Vitamin C has mass = 176 g

0.000142 mol of Vitamin C has mass  = 0.000142×176 = 0.025 g

Therefore, the mass of 0.000142 mol of Vitamin C is 0.025 g.

Learn more about the mole, here:

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If two reactant molecules collide with each other what two reasons might they not combine ?

Answers

Same poles like a magnet sometimes have

I need help with this!

Answers

Answer:

2.68 cm^3

Explanation:

Density= Mass/Volume

so...

8.96 g/cm^3 = 24.01 g/ V

and then u solve so it would be 2.68 cm ^3

((:

which temperature do they need to perform the experiment for perovskite to conduct electric current?


A: T=1980°C


B: T>1980°


C: T>_ 1980°C


D:T< 1980°C




For C it's suppose to be an less than equal sign .

Answers

Answer:

Correct answer is D : T <  1980°C

Explanation:

Correct answer is D:T< 1980°C

Perovskite proton conductors belong to the class of high temperature proton conductors (HTPCs) , solid that conduct electricity by transporting H⁺ ions (protons ) at temperatures above ambient , typically 400 - 1000°C

So, we get T < 1980°C

the law of conservation of mass​

Answers

Answer: The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction.

Explanation:

Use the atom builder interactive to identify each nucleus. Two protons represented as purple spheres and one neutron represented as a white sphere.Two protons represented as purple spheres and four neutrons represented as white spheres.Four protons represented as purple spheres and three neutrons represented as white spheres. One proton represented as a purple sphere and two neutrons represented as white spheres.Four protons represented as purple spheres and two neutrons represented as white spheres.Three protons represented as purple spheres and four neutrons represented as white spheres. Answer Bank

Answers

Answer:

[tex]\frac{3}{2}He[/tex]

[tex]\frac{6}{2} He[/tex]

[tex]\frac{7}{4}Be[/tex]

[tex]\frac{3}{1} H[/tex]

[tex]\frac{6}{4}Be[/tex]

[tex]\frac{7}{3} Li[/tex]

Explanation:

In the first nucleus we are told that there are two protons and one neutron. Let us remember that the mass number = number of protons + number of neutrons.

This implies that, for the first specie the mass number is 3, for the second specie the mass number is 6 and the third specie has a mass number of 7 and so on. The mass number is indicated as a superscript.

The atomic number is the number of protons in the nucleus of the atom and helps us to identify the atom. It is always written as a subscript as shown.

Write the equilibrium expression of each chemical equation.
2H2S(g) 2H2(g) + S2(g)

Answers

Answer:

[H2]2[S2][H2S]2Kc=[H2]2[S2][H2S]2

Explanation:

2H2S(g)⇋2H2(g)+S2(g)2H2S(g)⇋2H2(g)+S2(g)

The equilibrium constant expression in terms of concentrations is:

Kc=[H2]2[S2][H2S]2Kc=[H2]2[S2][H2S]2.

The equilibrium expression for the given reaction can be written in terms of equilibrium constant which is the ratio of power of molar concentration of the product to the product of power of molar concentration of the reactants.

What is equilibrium?

Equilibrium is a state for a reversible reaction where, the rate of forward reaction is equal to the rate of backward reaction. The rate of a reaction is the rate of decrease in the concentration of reactants or the rate of increase in the concentration of the products.

The given reaction at equilibrium state is written as:

[tex]\rm 2H_{2}S (g)\leftrightharpoons 2H_{2} (g)+ S_{2}(g)[/tex]

The equilibrium constant Kb is ratio of power of molar concentration of the product to the product of power of molar concentration of the reactants.

[tex]Kb = \rm \frac{[H_{2}S]^{2}}{[H_{2}]^{2} [S_{2}]}[/tex]

The rate of the reaction will be r = Kb [H₂]² [S₂].

To find more on equilibrium constant, refer here:

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A molten sample of 1.00kg of iron with a specific heat of 0.385J/g.K at 1000.K is immersed in a sample of water. If the water absorbs 270 kJ of heat what is the final temperature of the iron?
I need all the process.

Answers

Answer:

298. 7 K.

Explanation:

Hello!

In this case, since equation we use to compute the heat in a cooling or heating process is:

[tex]Q=mC(T_f-T_i)[/tex]

Whereas we are given the heat, mass, specific heat and initial temperature. Thus, we infer that we need to solve for the final temperature just as shown below:

[tex]T_f=T_i+\frac{Q}{mC}\\\\T_f=1000 K+\frac{-270000J}{1000g*0.385\frac{J}{g*K} } \\\\T_f=298.7 K[/tex]

It is important to notice that the iron release heat as water absorbs it, that is why it is taken negative.

Best regards!

Which of the following statements is false?
a. This class discussed four physical states of matter
b. An atom is the smallest particle of an element that still contains properties of the original element.
c. Gases can be colorless or colored
d. Mass is the measure of the earth’s gravitational attraction of a body
e. A pure substance has a fixed composition.

Answers

Answer:

d. Mass is the measure of the earth’s gravitational attraction of a body

This is FALSE. Mass is the measure of matter than an object contains.

Explanation:

b. An atom is the smallest particle of an element that still contains properties of the original element.

This is True

c. Gases can be colorless or colored

This is True

d. Mass is the measure of the earth’s gravitational attraction of a body

This is FALSE. Mass is the measure of matter than an object contains.

e. A pure substance has a fixed composition.

This is True.

Determine the chemical equation for the reaction between Fe3+ and Cu2+ with NH3

Answers

Answer:

Cu2 + 4 NH3 = Cu (NH3) 42+

so - - >

[Cu (NH3) 6] ^ 2+

Explanation:

How many grams of sulfur must be burned to give 100.0 g of So2

Answers

Answer:

50 g of S are needed

Explanation:

To star this, we begin from the reaction:

S(s) + O₂ (g) →  SO₂ (g)

If we burn 1 mol of sulfur with 1 mol of oxygen, we can produce 1 mol of sulfur dioxide. In conclussion, ratio is 1:1.

According to stoichiometry, we can determine the moles of sulfur dioxide produced.

100 g. 1mol / 64.06g = 1.56 moles

This 1.56 moles were orginated by the same amount of S, according to stoichiometry.

Let's convert the moles to mass

1.56 mol . 32.06g / mol = 50 g

Menthol is a crystalline substance with a peppermint taste and odor. When 0.533 g of menthol is dissolved in 25.0 g of cyclohexane, the freezing point of the solution is lowered by 2.84 ∘C. Look up the freezing point and f constant for cyclohexane in the Colligative Constants table. Calculate the molar mass of menthol.

Answers

Answer: The molar mass of menthol is 156.15 g/mol

Explanation:

Depression in freezing point is given by:

[tex]\Delta T_f=K_f\times m[/tex]

[tex]\Delta T_f=T_f^0-T_f=2.84^0C[/tex] = Depression in freezing point

[tex]K_f[/tex] = freezing point constant = [tex]20.8^0C/m[/tex]

m= molality

[tex]\Delta T_f=K_f\times \frac{\text{mass of solute}}{\text{molar mass of solute}\times \text{weight of solvent in kg}}[/tex]

Weight of solvent (cyclohexane)= 25.0 g = 0.025 kg  

Molar mass of solute (menthol) = ?

Mass of solute (menthol) = 0.533 g

[tex]2.84^0C=20.8\times \frac{0.533}{xg/mol\times 0.025}[/tex]

[tex]x=156.15g/mol[/tex]

The molar mass of menthol is 156.15 g/mol

What is the molecular formula of the molecule that has an empirical formula of C2H40 and a molar mass of 176.21 g/mol?
Type your answer using the following format:
CuCl2 for CuCl2.

Answers

Answer:

C8H16O4

Explanation:

C2H4O= 24+4+16

44

n=molar mass/empirical formula

n=176.21/44

=4

Therefore

Molar Formula= (C2H4O)4=C8H16O4

How many atoms of Kr (Krypton) are in a balloon that contains 2.00 mol of Kr? (4)

Answers

Answer:

[tex]atoms= 1.204x10^{24}atoms[/tex]

Explanation:

Hello!

In this case, according to the Avogadro's number, it is possible to compute the atoms of Kr in 2.00 moles as shown below:

[tex]atoms=2.00mol*\frac{6.022x10^{23}atoms}{1mol} \\\\atoms= 1.204x10^{24}atoms[/tex]

Best regards!

Name each of the following organic molecules. 

Answers

A. 2-Fluoro-3-Chlorohexane
B. 1-Bromo-2-Chloro-3-Fluorocyclopentane
C. 4-ethyl-5-methylhexane
D. 2,4,5-trimethylheptane

Convert 5.802 g/cm^3 to Kg/L

Answers

Answer:

5.80200 Kg / L

Explanation:

Liquid octane CH3CH26CH3 will react with gaseous oxygen O2 to produce gaseous carbon dioxide CO2 and gaseous water H2O. Suppose 2.3 g of octane is mixed with 12.4 g of oxygen. Calculate the minimum mass of octane that could be left over by the chemical reaction. Round your answer to 2 significant digits.

Answers

Answer: Octane will be used completely.

Explanation:

To calculate the moles :

[tex]\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}[/tex]    

[tex]\text{Moles of octane}=\frac{2.3g}{114g/mol}=0.0202moles[/tex]

[tex]\text{Moles of oxygen}=\frac{12.4g}{32g/mol}=0.388moles[/tex]

The balanced chemical reaction will be

[tex]2C_8H_{18}+25O_2(g)\rightarrow 16CO_2(g)+18H_2O(g)[/tex]  

According to stoichiometry :

2 moles of octane require = 25 moles of [tex]O_2[/tex]

Thus 0.0202 moles of octane will require=[tex]\frac{25}{2}\times 0.0202=0.2525moles[/tex]  of [tex]O_2[/tex]

Thus octane is the limiting reagent as it limits the formation of product and [tex]O_2[/tex] is the excess reagent.  

Thus octane will be used completely.

What is the ratio
amount (mol) Fatoms
amount (mol) Xe atoms
Enter your answer as an integer.
Pls help

Answers

Answer:

Empirical formula

Explanation:

The empirical formula of a compound is the simplest whole number ratio of atoms of each element in the compound. It is determined using data from experiments and therefore empirical.

Can someone help me with this

Answers

Answer:

wow!

5. C

6. B

7. B

8. A

Explanation:

I need help with this!!!

Answers

Answer:

0.73g/cm^3

Explanation:

d=m/v

d=11/15

d=0.73

Which of the following metals (M) will form an ionic compound with nitrogen with the general formula M3N2?

Answers

Answer:

There are no options provided dude,

But i guess the  answer will be a metal with valency 2 for sure as the subscript given for N in 'M3N2' is 2 so the valency of the metal u need to select will be 2 for sure

It can be magnesium or some other if the provided options in real question has Mg then its the answer

Please answer, this is due in 30 minutes

Answers

Answer:

0.591 g of magnesium phosphate is the theoretical yield.

Magnesium nitrate is the limiting reactant.

Explanation:

Hello!

In this case, since the balanced reaction turns out:

[tex]3Mg(NO_3)_2+2Na_3PO_4\rightarrow Mg_3(PO_4)_2+6NaNO_3[/tex]

Next, we compute the grams of magnesium phosphate yielded by each reactant, considering the present mole ratios and molar masses:

[tex]m_{Mg_3(PO_4)_2}^{by\ Mg(NO_3)_2}=1.00gMg(NO_3)_2*\frac{1molMg(NO_3)_2}{148.31gMg(NO_3)_2}*\frac{1molMg_3(PO_4)_2}{3molMg(NO_3)_2} *\frac{262.86gMg_3(PO_4)_2}{1molMg_3(PO_4)_2} \\\\m_{Mg_3(PO_4)_2}^{by\ Mg(NO_3)_2}= 0.591gMg_3(PO_4)_2\\\\m_{Mg_3(PO_4)_2}^{by\ Na_3PO_4}=1.00gNa_3PO_4*\frac{1molNa_3PO_4}{163.94gNa_3PO_4}*\frac{1molMg_3(PO_4)_2}{2molNa_3PO_4} *\frac{262.86gMg_3(PO_4)_2}{1molMg_3(PO_4)_2} \\\\m_{Mg_3(PO_4)_2}^{by\ Na_3PO_4} = 0.802gMg_3(PO_4)_2[/tex]

Thus, we infer that the correct theoretical yielded mass is 0.591 g as magnesium nitrate is the limiting reactant for which it produces the fewest grams of product.

However, is not possible to compute the percent yield since no actual yield is given, and must be provided or indicated by the problem or an experiment and it not here, nevertheless, you may compute the percent yield by dividing the actual yield by the theoretical and then multiplying by 100:

[tex]Y=\frac{actual}{0.591g}*100\%[/tex]

Best regards!

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