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kotegsom [21]
3 years ago
12

What effect does getting 8 hours of sleep have on 8th grade science test scores ?

Chemistry
1 answer:
abruzzese [7]3 years ago
7 0

Answer:

Getting 8 hours of sleep will make the test grades go up.

Explanation:

because the kids will not be tired in the morning.

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EXTRA POINTSSS 1. A solution at 25 degrees Celsius is 1.0 × 10–5 M H3O+. What is the concentration of OH– in this solution?
AlekseyPX

Answer:

Concentration of OH⁻:

1.0 × 10⁻⁹ M.

Explanation:

The following equilibrium goes on in aqueous solutions:

\text{H}_2\text{O}\;(l)\rightleftharpoons \text{H}^{+}\;(aq) + \text{OH}^{-}\;(aq).

The equilibrium constant for this reaction is called the self-ionization constant of water:

K_w = [\text{H}^{+}]\cdot[\text{OH}^{-}].

Note that water isn't part of this constant.

The value of K_w at 25 °C is 10^{-14}. How to memorize this value?

  • The pH of pure water at 25 °C is 7.
  • [\text{H}^{+}] = 10^{-\text{pH}} = 10^{-7}\;\text{mol}\cdot\text{dm}^{-3}
  • However, [\text{OH}^{-}] = [\text{H}^{+}]=10^{-7}\;\text{mol}\cdot\text{dm}^{-3} for pure water.
  • As a result, K_w = [\text{H}^{+}] \cdot[\text{OH}^{-}] = (10^{-7})^{2} = 10^{-14} at 25 °C.

Back to this question. [\text{H}^{+}] is given. 25 °C implies that K_w = 10^{-14}. As a result,

\displaystyle [\text{OH}^{-}] = \frac{K_w}{[\text{H}^{+}]} = \frac{10^{-14}}{1.0\times 10^{-5}} = 10^{-9} \;\text{mol}\cdot\text{dm}^{-3}.

8 0
3 years ago
Describe how and why the statue of the Sphinx has changed since it<br>was made.​
Lyrx [107]

Answer:

I don't know if this will help but. The Great Sphinx has suffered from erosion and vandalism. Hatshepsut's stepson was too young to rule at the time of her husband's death, so she just took the job.

8 0
3 years ago
Nitrogen has an average atomic mass of 14.00674. it has two isotopes, n-14 and n-15, with atomic masses of 14.0031 amu and 15.00
masya89 [10]
In this case, we are going to assume that there are 100 atoms to make things easier. 

Let R% be the abundance of n-15. With this in mind, we calculate the abundance of n-14 to be 100%-R%

14.0031*(100-R)% + 15.001 * R%= 14.00674 
In this case, we can delete or ignore the % sign since we do not want to carry it around, however, we need to keep in mind that the final answer is in %

14.0031*(100-R) + 15.001 * R= 14.00674 
1400.31-14.0031R+15.001R=1400.674
0.9979R=0.364
R=0.3648

Then, the abundance of n-15 is 0.3648%

5 0
3 years ago
A student observes two strips of magnesium, mg ribbon that are each 3cm long. One strip of magnesium
ankoles [38]

Therefore option c , i.e. The substances in both test tubes are reactive only at high temperatures. is the only statement which is NOT supported by the student's observations.

<h3>What is the reaction between Magnesium and Hydrogen ?</h3>

Magnesium reacts with hydrochloric acid to produce hydrogen gas

Mg (s) + 2 HCl (aq) → MgCl₂ (aq) + H₂ (g)

In this reaction, the magnesium and acid are gradually used up , which can be seen in the test tube 2 .

A chemical reaction is taking place in Test tube 2 ,

Hydrogen gas is released in test tube 2 ,

Energy is released in the reaction involving hydrochloric acid and we can see in test tube 2 the reaction is going on

therefore option C i.e. The substances in both test tubes are reactive only at high temperatures. is the only statement which is NOT supported by the student's observation.

To know more about the chemical reaction between Magnesium and Hydrogen and this test.

brainly.com/question/19062002

#SPJ4

6 0
2 years ago
Which enzyme "unzips" DNA by breaking hydrogen bonds that hold the bases together?
KonstantinChe [14]
A- *enzyme* helicase
4 0
3 years ago
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