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mamaluj [8]
3 years ago
8

Why are dark matter and dark energy described as "dark"? A. Because they emit blackbody radiation. B. Because they absorb light.

C. Because they are only found in shadows. D. Because we cannot easily detect them.
HELP ME PLZ!!
Chemistry
1 answer:
VMariaS [17]3 years ago
8 0

Answer:

D. Because we cannot easily detect them.  

Explanation:

Dark matter are called dark because using existing astronomical instruments we are blinded to them. Dark matter and dark energy are difficult to detect and properly observe. As we know that the whole universe is made up of matter, some of the matter do not interact with the electromagnetic radiations which makes undetectable.

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During lab, a student used a Mohr pipet to add the following solutions into a 25 mL volumetric flask. They calculated the final
kompoz [17]

Answer:

(FeSCN⁺²) = 0.11 mM

Explanation:

Fe ( NO3)3 (aq) [0.200M] + KSCN (aq) [ 0.002M] ⇒ FeSCN+2

M (Fe(NO₃)₃  = 0.200 M

V (Fe(NO₃)₃ =  10.63 mL

n (Fe(NO₃)₃ = 0.200*10.63 = 2.126 mmol

M (KSCN) =  0.00200 M

V (KSCN) = 1.42 mL

n (KSCN) =  0.00200 * 1.42 = 0.00284 mmol

Total volume = V (Fe(NO₃)₃  + V (KSCN)

                       = 10.63 + 1.42

                       = 12.05 mL

Limiting reactant = KSCN

So,

FeSCN⁺² = 0.00284 mmol

M (FeSCN⁺²) = 0.00284/12.05

                     = 0.000236 M

Excess reactant = (Fe(NO₃)₃

n(Fe(NO₃)₃ =  2.126 mmol -  0.00284 mmol

                  =2.123 mmol

For standard 2:

n (FeSCN⁺²) = 0.000236 * 4.63

                    =0.00109

V(standard 2) = 4.63 + 5.17

                       = 9.8 mL

M (FeSCN⁺²)  = 0.00109/9.8

                      = 0.000111 M = 0.11 mM

Therefore, (FeSCN⁺²) = 0.11 mM

7 0
3 years ago
Estimate the heat of neutralization of H3PO4 in kJ/mol given these data: Heat transferred = 2.5 x 102 J Moles of H3PO4 = 1.4 x 1
OlgaM077 [116]
Below are the steps to get the answers:

<span>1.) write out the balance equation 3NaOh+H3PO4->Na3PO4+3H2O
 
2.) You are given everything needed to calculate q=heat transfer=2.2*10^2, H3PO4 moles= 1.5*10^-3, NaOH moles=5.0*10^-3
 
3.) equation is deltaHneutraliztion=q/Moles of limiting reagent H3PO4 is limiting reagent because lowest moles, and is used up first
 
4.) Now plug in variables DeltaH=2.2*10^2(1.5*10^3)= 146.67kj/mole Notice we had to convert J to kj, </span>
7 0
3 years ago
You have 8 moles of a gas at 250 K in a 6 L container. What is the pressure of the gas? Show your work
Bogdan [553]

Hello:

In this case, we will use the Clapeyron equation:

P = ?

n = 8 moles

T = 250 K

R = 0.082 atm.L/mol.K

V = 6 L

Therefore:

P * V = n *  R * T

P * 6 = 8 * 0.082* 250

P* 6 = 164

P = 164 / 6

P = 27.33 atm


Hope that helps!

7 0
4 years ago
Suppose you need to prepare 141.9 mL of a 0.223 M aqueous solution of NaCl. What mass of NaCl do you need to use to make the sol
Afina-wow [57]

Answer:

1.811 g

Explanation:

The computation of the mass need to use to make the solution is shown below:

We know that molarity is

Molarity = \frac{Number\ of\ moles}{Volume\ in\ L}

So,

Number\ of\ moles = Molarity\ \times Volume\ in\ L

= 0.223\times 0.141

= 0.031 moles

Now

Mass = moles \times Molecualr\ weight

where,

The Molecular weight of NaCl is 58.44 g/mole

And, the moles are  0.031 moles

So, the mass of NaCL is

= 0.031 \times 58.44

= 1.811 g

We simply applied the above formulas

3 0
3 years ago
All of the substances on the periodic table are classified as elements except
zzz [600]

Answer: all elements in the periodic table is classified as elements

Explanation:

The structure of the table shows periodic trends. The seven rows of the table, called periods, generally have metals on the left and nonmetals on the right. The columns, called groups, contain elements with similar chemical behaviours. Six groups have accepted names as well as assigned numbers: for example, group 17 elements are the halogens; and group 18 are the noble gases

6 0
4 years ago
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