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Yuri [45]
3 years ago
14

Taking a nap in the afternoon makes people more focused for the rest of the day.

Chemistry
2 answers:
Viktor [21]3 years ago
8 0

Answer:

dependent

Explanation:

it help them focus better

julia-pushkina [17]3 years ago
4 0
The answer to your question is Dependent.
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Who established atomic numbers as the basis for organizing the periodic table?
Jobisdone [24]

Answer:

Henry Moseley.

Explanation:

Hello,

Henry Moseley's work stated that it is better to organize the periodic table in the light of the atomic number (which accounts for the amount of protons and electrons) instead of the atomic mass, because atomic numbers are not arbitrarily assigned as long as they have the aforesaid physical basis.

Best regards.

3 0
3 years ago
A chemist dissolves 239 mg of pure potassium hydroxide in enough water to make up of solution. Calculate the pH of the solution.
PSYCHO15rus [73]

Answer: the pH is 11.78

Explanation:Please see attachment for explanation

7 0
3 years ago
Which can be classified as a trace fossil
dexar [7]

Trace fossils provide us with indirect evidence of life in the past, such as the footprints, tracks, burrows, borings, and feces left behind by animals, rather than the preserved remains of the body of the actual animal itself. so i would say B.

6 0
3 years ago
Read 2 more answers
Commercial concentrated aqueous ammonia is 28% nh3 by mass and has a density of 0.90 g/ml. what is the concentration of ammonia
patriot [66]

Answer:- 14.9 M

Solution:- Given commercial sample of ammonia is 28% by mass. Let's say we have 100 grams of the sample. Then mass of ammonia would be 28 grams.

Density of the solution is given as 0.90 grams per mL.

From the mass and density we could calculate the volume of the solution as:

100g(\frac{1mL}{0.90g})

= 111 mL

Let's convert the volume from mL to L as molarity is moles of solute per liter of solution.

111mL(\frac{1L}{1000mL})  

= 0.111 L

Now, we convert grams of ammonia to moles on dividing the grams by molar mass. Molar mass of ammonia is 17 gram per mole.

28g(\frac{1mole}{17g})

= 1.65 mole

To calculate the molarity we divide the moles of ammonia by the liters of solution:

molarity=\frac{1.65mole}{0.111L}

= 14.9 M

So, the molarity of the given commercial sample of ammonia is 14.9 M.

5 0
3 years ago
PLEASE HELP!!!!!!!
dsp73

Answer: 1. 2Al+3CuCl_2\rightarrow 2AlCl_3+3Cu

2. 3 moles of CuCl_2 : 2 moles of Al

3. 0.33 moles of CuCl_2 : 0.92 moles of Al

4. CuCl_2 is the limiting reagent and Al is the excess reagent.

5. Theoretical yield of AlCl_3 is 29.3 g

Explanation:

To calculate the moles :

\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}    

\text{Moles of} Al=\frac{25.0g}{27g/mol}=0.92moles

\text{Moles of} CuCl_2=\frac{45.0g}{134g/mol}=0.33moles

The balanced chemical equation is:

2Al+3CuCl_2\rightarrow 2AlCl_3+3Cu  

According to stoichiometry :

3 moles of CuCl_2 require = 2 moles of Al

Thus 0.33 moles of CuCl_2 will require=\frac{2}{3}\times 0.33=0.22moles  of Al

Thus CuCl_2 is the limiting reagent as it limits the formation of product and Al is the excess reagent.

As 3 moles of CuCl_2 give = 2 moles of AlCl_3

Thus 0.33 moles of CuCl_2 give =\frac{2}{3}\times 0.33=0.22moles  of AlCl_3

Theoretical yield of AlCl_3=moles\times {\text {Molar mass}}=0.22moles\times 133.34g/mol=29.3

Thus 29.3 g of aluminium chloride is formed.

5 0
2 years ago
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