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SOVA2 [1]
3 years ago
6

the law of conversation of (mass/energy) states that the total mass before a chemical reaction is the same as the totally mass a

fter the reaction. which is one is it mass or energy??
Chemistry
1 answer:
Nimfa-mama [501]3 years ago
5 0

The law of conservation of mass says that matter cannot be created or destroyed by ordinary chemical or physical changes.

This means:

The mass will be the same before and after the chemical or physical change

There are the same number of each type of atom before and after the change

The total mass of all components of a chemical reaction or physical change can be measured before and after the change to demonstrate that the mass is constant.

Scientists believe that energy is conserved, like mass, during a physical or chemical change. The law of conservation of energy says that energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical changes.

Energy can be more challenging for scientists to keep track of during a chemical reaction than mass. Mass is able to be measured on a balance before and after the change, but scientists must use more advanced techniques to measure the energy in a system.

Energy is converted from one form to another during a chemical change.This energy is not created or destroyed; it is just converted from one form of energy to another during the chemical and physical changes that occur.

Physical Change: In a physical change, atoms are rearranged but remain in the same sample of matter. The same numbers of atoms are present before and after the change, and they have the same total mass. Atoms are spread farther apart or pushed closer together during a phase change. When a substance changes phases, the volume may change but the mass doesn't.

Chemical Change: In a chemical change, the original bonds are broken and new bonds are formed. The same atoms are present before and after a chemical change, they are just rearranged to make different compounds.

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Use the data in the table above to calculate an approximate ΔH∘ in kilojoules for the synthesis of hydrazine from ammonia:
ankoles [38]
DeltaH formation = deltaH of broken bonds - deltaH of formed bonds

Broken bonds: tiple bond N-N and H-H bond
Formed bonds: N-H and N-N bonds

You also have to take note of the molar coefficients

deltaH formation = <span> [(N≡N) + 2 * (H-H)] - [4 * (N-H) + (N-N)] 
                           = (945 + 2*436) - (4*390 + 240)
                            = 17 kJ/mol

The answer is 17 kJ/mol.</span>
8 0
3 years ago
What describes a change in velocity?
siniylev [52]
Acceleration can be described as changes in speed, changes in direction, or changes in both. Acceleration is a vector.
4 0
3 years ago
Read 2 more answers
Consider the following reaction mechanism:
snow_lady [41]

Answer:

  • <em><u>Step 2 (the slow step).</u></em>

Explanation:

The rate-determining step is always the slow step of a mechanism.

That is so, because it is the slow step which limits the reaction.

Imaging that for assembling a toy you have process of three steps:

  • 1. order ten pieces, which you can do in 1 minute: meaning that you can order order the pieces for 60/1 = 60 toys in 1 hour.

  • 2. glue the pieces and hold the toy until the glue hardens, which takes 1 hour: meaning finishingh 1 toy in 1 hour.

  • 3. pack the toy, which takes 2 minutes: meaning that you can pack 60/2 = 30 toys in one hour.

The time to glue and hold one toy until the glue hardens determines that you can assemble 1 toy in 1 hour and not 60 toys or 30 toys.

Thus, the step that determines the rate at which the reaction happens is the slowest step: step 2.

3 0
2 years ago
Read 2 more answers
Use MO diagrams to place B2+, B2, and B2- in order of (a) decreasing bond energy; (b) decreasing bond length.
shepuryov [24]

We use the MO diagram for a homonuclear diatomic species (since C and N are neighbours, we treat them as the "same").

The first two electrons contribute to bonding. The next two are anti-bonding.

The next six contribute to bonding, and the following six are anti-bonding.

So, if we start with CN+, which has 4+5-1 (8) valence electrons, we note that the first two electrons contribute to bonding, while the next two cancel this out; the next four contribute to bonding, so the bond order is 4/2 = 2.

If we add one more electron to get CN, there are now 5 bonding electrons, giving bond order 5/2=2.5.

Adding one more to give CN- would give the bond order 6/2 = 3. (If we added more electrons, each one would lower the bond order.)

Given a series of molecules with identical skeletal structures, the one with the highest bond order has the highest bond energy:

CN+ < CN < CN-

Lewis structures will verify that CN- has a triple bond, but they do not work particularly well for CN+ and CN.

learn more about bond orders at

brainly.com/question/9713842

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3 0
1 year ago
Draw the alkene formed when 1-heptyne is treated with hbr in the presence of peroxide.
Nimfa-mama [501]
<h2>Heptene formed is -</h2><h2>CH_3-CH_2-CH_2-CH_2-CH_2-CH=CHBr</h2>

Explanation:

The two possibilities when the peroxide is not present

  • CH_{3}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-C≡CH +HBr → CH_3-CH_2-CH_2-CH_2-CH_2-CBr=CH_{2}

  • CH_3-CH_2-CH_2-CH_2-CH_2-CBr=CH_2 + HBr →CH_3-CH_2-CH_2-CH_2-CH_2-CBr_2-CH_3

In presence peroxide,

CH_3-CH_2-CH_2-CH_2-CH_2-C≡CH+ HBr →CH_3-CH_2-CH_2-CH_2-CH_2-CH=CHBr

  • When peroxides are present in the reaction mixture, hydrogen bromide adds to the triple bond of heptane with regioselectivity.
  • This reaction is opposite to that of Markovnikov's rule which says that when asymmetrical alkene reacts with a protic acid HX, then the hydrogen of an acid is attached to the carbon with more in number of hydrogen substituents, and the halide (X) group is attached to the carbon with more in number of substituents of alkyl.
  • One mole of HBr adds to one mole of 1-heptane.
  • The structure of heptene formed is -

CH_3-CH_2-CH_2-CH_2-CH_2-CH=CHBr

5 0
3 years ago
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