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3 years ago

15

Astronomers think planets formed from interstellar dust and gases that clumped together in a process called _____. A. stellar ev

olution B. nebular aggregation C. planetary accretion D. nuclear fusion

1 answer:

Akimi4 [234]3 years ago

6 0

Your answer is stellar evolution

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If there is a graduated cylinder containing 20mL of water and a small rock is gently placed inside it, and the water level insid

LekaFEV [45]

Answer:

5

Explanation:

just subtract 20-25 and 5 is left over which is how much the water when up with the rock.

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Calculate the speed of a dog running through a field if he is covering 23.7 meters in 54 seconds.

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Explanation:

speed = distance/time

= 23.7/54 m/s

= 0.44 m/s

speed of a dog running through a field = 0.44 m/s

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You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.8

Lubov Fominskaja [6]

Complete Question

You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.82 when exactly 13 mL of base had been added, you notice that the concentration of the unknown acid was 0.1 M. What is the pKa of your unknown acid?

Answer:

The pK_a value is $pK_a =7.82$

Explanation:

From the question we are told

The volume of base is $V_B = 26.mL = 0.0260L$

The pH of solution is $pH = 7.82$

The concentration of the acid is $C_A = 0.1M$

From the pH we can see that the titration is between a strong base and a weak acid

Let assume that the the volume of acid is $V_A = 18mL= 0.018L$

Generally the concentration of base

$C_B = \frac{C_AV_A}{C_B}$

Substituting value

$C_B = \frac{0.1 * 0.01800}{0.0260}$

$C_B= 0.0692M$

When 13mL of the base is added a buffer is formed

The chemical equation of the reaction is

$HA_{(aq)} + OH^-_{(aq)} --------> A^{+}_{(aq)} + H_2 O_{(l)}$

Now before the reaction the number of mole of base is

$No \ of \ moles[N_B] = C_B * V_B$

Substituting value

$N_B = 0.01300 * 0.0692$

$= 0.0009 \ moles$

Now before the reaction the number of mole of acid is

$No \ of \ moles = C_B * V_B$

Substituting value

$N_A = 0.01800 *0.1$

$= 0.001800 \ moles$

Now after the reaction the number of moles of base is zero i.e has been used up

this mathematically represented as

$N_B ' = N_B - N_B = 0$

The number of moles of acid is

$N_A ' = N_A - N_B$

$= 0.0009\ moles$

The pH of this reaction can be mathematically represented as

$pH = pK_a + log \frac{[base]}{[acid]}$

Substituting values

$7.82 = pK_a +log \frac{0.0009}{0.0009}$

$pK_a =7.82$

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3 years ago

What type of bond is made between amino acids in the ribosome?

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Answer:

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Planetesimals are made from <br><br> A. Rock<br><br> B. Gas<br><br> C. Stars<br><br> D. Clouds

White raven [17]

A )rock is correct answer

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