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Tamiku [17]
3 years ago
7

A potassium isotope has a half-life of 1.25 billion years. Given that scientists estimate Earth's age to be 4.6 billion years, w

hat is the most likely percentage of parent to daughter isotopes of this element currently existing on Earth?
Less than 10 percent
25 percent
50 percent
More than 75 percent
Chemistry
1 answer:
dmitriy555 [2]3 years ago
8 0

Answer:

More than 75%

Explanation:

2.5billion -> 1.25Billion

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Which correctly lists three characteristics of minerals?
maria [59]

Answer:

The answer is A  hope this helps

Explanation:

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4 years ago
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According to the periodic table, which of these elements will form an ion with a –2 charge? calcium
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Answer:

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6 0
3 years ago
Write ionic equations for the following:<br> HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
vodomira [7]

Answer:

HCl(aq) + KOH(aq) ===> H2O(l) + KCl(aq)

Note the stoichiometry of the balanced equations shows us that HCl and KOH react in a 1:1 mole ratio. So, let us find moles of HCl and moles of KOH that are present:

moles HCl = 250.0 ml x 1 L/1000 ml x 0.25 mol/L = 0.06250 moles HCl

moles KOH = 200.0 ml x 1 L/1000 ml x 0.40 mol/L = 0.0800 moles KOH

You can see that there are more moles of KOH than there are of HCl, meaning that KOH is in excess and after neutralizing all of the HCl, the solution will be left with excess KOH making the pH > 7 = BASIC

4 0
2 years ago
You have 500.0 ml of a buffer solution containing 0.30 m acetic acid (ch3cooh) and 0.20 m sodium acetate (ch3coona). what will t
Nataly [62]
First, we should get moles acetic acid = molarity * volume

                                                                =0.3 M * 0.5 L

                                                                =  0.15 mol

then, we should get moles acetate = molarity * volume

                                                           = 0.2 M * 0.5L

                                                           = 0.1 mol

then, we have to get moles of OH- which added:

moles OH- = molarity  * volume

                   = 1 M    * 0.02L

                  = 0.02 mol

when the reaction equation is:


                 CH3COOH  +  OH-  → CH3COO-   +  H2O


moles acetic acid after adding OH- = (0.15-0.02) 
                                             
                                                            =  0.13M                                       

moles acetate after adding OH- =  (0.1 + 0.02)

                                                      =   0.12 M

Total volume = 0.5 L + 0.02 L= 0.52 L

∴[acetic acid] = moles acetic acid after adding OH- / total volume

                        = 0.13mol / 0.52L

                       = 0.25 M

and [acetate ) = 0.12 mol / 0.52L
 
                        = 0.23 M

by using H-H equation we can get PH:

PH = Pka + ㏒[salt/acid]

when we have Ka = 1.8 x 10^-5

∴Pka = -㏒Ka 

        = -㏒ 1.8 x 10^-5

       = 4.7

So by substitution:

∴ PH = 4.7 + ㏒[acetate/acetic acid]

         = 4.7 + ㏒(0.23/0.25)

        = 4.66
6 0
3 years ago
Which of the following statements about air masses is true?
aleksandrvk [35]

Answer:

The correct answer is: D. Air masses are created by patterns of heating and cooling of the Earth's surface.

Explanation:

The air masses can be simply be divided into warm and cold ones, further they can be moist or not. The formation of the air masses, be it warm and cold, over the land masses is because of patterns of heating and cooling. This results some areas to produce very large air masses that are cold and dry, like Siberia, or warm and dry large air masses, like Sahara. Also, on a local level there's air masses that develop every day and night, which is noticeable during the night and the morning, where the colder air masses from the mountains move down to the valleys, and the warm air masses from the valleys move up to the mountains. That is a because of the change in the heating and cooling patters that differ during the day and the night.

4 0
3 years ago
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