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ryzh [129]
3 years ago
7

Why does the rate of most reactions decrease over time?

Chemistry
1 answer:
ratelena [41]3 years ago
3 0

Answer:

ExplanaA) A decrease in reactant concentration reduces the frequency of successful collisions.  tion:

As a reactant gets used up, there are fewer molecules present to collide with others. A reaction depends on molecular collisions. When there are fewer collisions, the reaction slows down.

B) is wrong. A reaction is usually carried out at constant temperature,

C) is wrong. Not all reactions need catalysts.

D) is wrong. If the temperature is constant, pressure will have little effect on the movement and energy of molecule.

You might be interested in
Intermolecular forces do not have any effect on determining the physical properties of
djyliett [7]

Answer:

False

Explanation:

The physical properties of melting point, boiling point, vapor pressure, evaporation, viscosity, surface tension, and solubility are related to the strength of attractive forces between molecules. These attractive forces are called Intermolecular Forces.

6 0
3 years ago
A sample of CO2 gas has a volume of 2.7 L at 78.5 kPa. At what pressure would this sample of gas have a volume of 4.0L? Temperat
lisabon 2012 [21]

Answer:

52.99 kPa

Explanation:

Initial volume V1 = 2.7 L

Initial Pressure P1 = 78.5 kPa

Final Volume V2 = 4.0L

Final Pressure P2 = ?

Temperature is constant

The relationship between these quantities is given by the mathematical expression of Boyles law. This is given as;

V1P1 = V2P2

P2 = V1P1 / V2

P2 = 2.7 * 78.5 /  4.0

P2 = 52.99 kPa

7 0
3 years ago
5pts. Chemistry multiple choice​
aleksandrvk [35]

Answer:

C. Xenon

Explanation:

The question only requires you to use your visual skills to identify the unknown gas. Look at the spectra of unknown gas and xenon, are they not identical? SInce they are same, the unknown sample must be xenon.

4 0
2 years ago
Read 2 more answers
1. Using the Slater rule, determine the effective nuclear charge of platinum.
AleksandrR [38]

Answer:

Z* = 3.55

Explanation:

Slater rule says that:

Z*= Z - S

Z* be the nuclear effective charge

Z is the nuclear charge

S is the shielding constant

First we write the electronic configuration of platinum:1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{10} 4s^{2} 4p^{6} 4d^{10} 5s^{2} 5p^{6} 4f^{14} 5d^{9} 6s^{1}

The first Slater rule says that we need to group:

(1s^{2}) (2s, 2p)^{8} (3s, 3p)^{8} (3d^{10}) (4s, 4p)^{8} (4d^{10}) (5s, 5p)^{8} (4f^{14}) (5d^{9}) (6s^{1})

The second rule says that the electrons to the right are not shielding, but we are going to solve the exercise for the last level (6s), so we don't have electrons to the right.

For the third rule we have two considerations, if is ns or np and if is nd or nf:

For our case, we have an electro that is in ns, so the rule says that

-electrons within same group shield 0.35, except the 1s which shield 0.30

-electrons within the n-1 group shield 0.85

-electrons within the n-2 or lower groups shield 1.00

Now we can proceed with the calculation:

The first consideration in the third rule does not apply as we only have one electron on this level.

The second consideration will be as follow for the level 5, where we have 17 electrons.

Finally the third consideration will be for levels 1, 2, 3 and 4, where we have 14 for 4f, 10 for 4d, 8 for 4s and 4p, 10 for 3d, 8 for 3s and 3p, 8 for 2s and 2p and finally 2 for 1s, which gives 60 electrons.

So the result for S=(60*1.00 + 17*0.85) = 74.45

And the equation is: Z* = 78 - 74.45

So Z* = 3.55

3 0
3 years ago
Read the sentence.
ExtremeBDS [4]

Answer:

The correct answer is "reveal the structures".

Explanation:

The predicate is the part of the prayer that tells us what the subject is doing. In this prayer "The Fossils" is the subject, so we must seek the action that develops from the subject. That action is that the fossils "reveal the structures". In this way, we can find the simple predicate of this sentence.

Have a nice day!

3 0
3 years ago
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