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Oliga [24]
2 years ago
14

Without the atmosphere, life on Earth would not be possible. Which of the following is NOT an explanation for how Earth’s atmosp

here protects life on the planet?
A. It allows visible light to pass through completely.


B. It contains gases that filter out ultraviolet radiation.

C. It keeps Earth warm by trapping in heat.

D. It protects life from ultraviolet rays of light
Chemistry
2 answers:
kvasek [131]2 years ago
3 0

Answer:

B

Explanation:

IM A CHEMISTRY WIZZZZ

:)

I hope u get full marks on your paper/test/quiz or whatever!

There is a 20 percent chance so stay positive!

Alex73 [517]2 years ago
3 0

Answer:

D

Explanation: ultraviolet rays are harmful to humans

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The following calculations must be handwritten in your notebook. – Acetic Acid ■ Hydrogen ion concentration ■ Ka ■ % Error – Ace
Nikitich [7]

Answer:

Explanation:

1) Acetic acid

Concentration is given as 0.103 M

The average pH of this solution = 2.96

we know that pH = - log [H+] therefore [H+] = 10-pH

[H+] = 10-2.96

= 1.1 x 10-3 M = 0.0011 M

Consider the equilibrium

CH3COOH ⇄CH3COO- + H+

Initial 0.103 0 0

Change -x +x +x

equlibrium 0.103 -x x x

Ka = x2 / 0.103 - x

Here the initial concentration of CH3COOH = 0.103 M

the equilibrium concentration of H+ = x = 0.0011 M

Therefore the equilibrium conc of acetic acid = 0.103 - 0.0011 = 0.1019 M

Therefore Ka = 0.0011 x 0.0011 / 0.1019 = 1.187 x 10-5

2) Acetic acid + NaOH

pH measured = 4.48 , therefore [H+} = 10-4.48 = 3.3 x 10-5

Volume and conc of acetic acid = 10 mL of 0.103 M

= 10 mL x 0.103 mmol / mL

= 1.03 mmol

Volume and conc of NaOH added = 4 mL of 0.0992 M

= 4 x 0.0992 mmol

= 0.397 mmol

Consider the equation

CH3COOH + NaOH -----------> CH3COONa + H2O

Initial 1.03 0.397 0

Final 0.633 0 0.397

0.397 mmole of NaOH will convert 0.397 mmole of acetic acid to sodium acetate.

Thus the final moles of acetic acid and sodium acetate in the solution are 0.633 and 0.397

therefore [salt] / [acid] = 0.397 / 0.633 = 0.627

By Hendersen equation pH = pKa + log[salt / acid]

pH = pKa + log 0.627 = pKa - 0.203

or pKa = pH + 0.203 = 4.48 + 0.203 [ since the measured pH = 4.48]

= 4.683

Ka = 10-4.683 = 2.07 x 10-5

3) Phosphate salts:

(i) mass of NaH2PO4 taken = 0.613 g

molar mass of NaH2PO4 = 120

therefore moles = 0.613 / 120 = 0.0051 mole

= 5.1 mmol

The volume is 30 mL therefore concentration = 5.1 /30 mmol/mL

= 0.17 M

consider the equilibrium

H2PO4-⇄ HPO42- + H+

Initial 0.17 0 0

Change -x +x + x

equilibrium 0.17-x x x

Ka = x2 / 0.17-x = 6.2 x 10-8 [ Ka is given]

neglect x in the denominator as it is very small x2 = 0.17 x 6.2 x 10-8

x =  1.03 x 10-4

Thus the equilirium conc of H+ = 1.03 x 10-4 therefore pH = - log 1.03 x 10-4 = 3.99

(ii) Mass of Na2HPO4.7H2O =0.601 g

therefore no of moles = 0.601 / 268.07 = 0.00224 mole

= 2.24 mmol

The volume = 30 mL , therefore conc = 2.24 / 30 mmol/ml

= 0.075 M

consider the equilibrium

HPO42- ⇄ PO43- + H+

Initial 0.075 0 0

Change -x +x + x

equilibrium 0.075-x x x

Ka = x2 / 0.075-x = 4.8 x 10-13 [ Ka is given]

neglect x in the denominator as it is very small x2 = 0.075 x 4.8 x 10-13

x =  1.9 x 10-7

Thus the equilirium conce of H+ = 1.9 x 10-7 therefore pH = - log 1.9 x 10-7 = 6.7

(iii) Mass of Na3PO4.12H2O taken = 0.208 g

moles of trisodiumphosphate 0.208/ 380 = 0.00055 moles

= 0.55 mmol

Volume = 10 mL therefore conc = 0.55/10 = 0.055 mmol/mL

= 0.055 M

Consider the equilibrium reaction

PO43- + H2O  ⇄ HPO42- + OH-

initial 0.055 0 0

Change -x +x +x

equilibrium 0.055-x x x

Kb = x2/ 0.055 -x = 0.0208 [Kb = Kw / Ka = 10-14 / 4.8 x 10-13 = 0.0208]

x2 + 0.0208x - 0.001144 = 0 Solving this equation we get x = 0.025

That is the conce of OH- ion = 0.025M

Therefore pH = 14 - pOH = 14 - 1.6 =12.4

3 0
2 years ago
Density of water is 1 g/ml. If a piece of wood with a density of 5 g/ml is
Alchen [17]

Answer:

The piece of wood will sink

Explanation:

If an object has a density higher than water, it will sink, and the piece of wood is more dense than water when measured.

6 0
2 years ago
Why was Newland’s periodic table rejected?
Rina8888 [55]
He put iron with sulfur and oxygen and it had a few more errors and iron is a metal the other two are nonmetals

5 0
3 years ago
Akosua has observed that anytime she drinks sobolo, her stool appears dark green. On one occasion
Anna007 [38]

Answer:

i. Sobolo is a Ghanian drink that is produced from red hibiscus flower that has an average pH of 6.7

It contains cyanidin and anthocyanins, which is a red pigment that is red in an acidic medium and changes green when introduced in a basic medium that has a high pH

The pH at the rectum of the digestive system = 5 to 8 (Slightly basic)

Therefore, what made the stool of Akosua green is that the sobolo drink changes to green in basic solution

ii. The stool which appeared green because she took sobolo turn into bright red upon mixing with the acidic WC water because of the presence of anthocyanins in sobolo, it turns red in an acidic medium

iii. Sobolo which turns green, or blue in a basic medium and red in an acidic medium can be used as a litmus solution to test the pH of a given substance

Explanation:

Sobolo or soobolo in Ghana is a name for the Hibiscus tea or tisane, which is made from calyces of the hibiscus plant, and has a sour (tangy) taste and appears bright red in color

8 0
3 years ago
Write a paragraph
steposvetlana [31]
I think It’s 55 but that’s just me
6 0
3 years ago
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