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Damm [24]
3 years ago
15

Explain how a star does not get too hot or too cold

Chemistry
1 answer:
Jet001 [13]3 years ago
6 0

its a ball of fire that burn till it dies it is always around the same temperature

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If the K a Ka of a monoprotic weak acid is 7.3 × 10 − 6 , 7.3×10−6, what is the pH pH of a 0.40 M 0.40 M solution of this acid?
olga_2 [115]

Answer:

pH =3.8

Explanation:

Lets call the monoprotic weak acid HA, the dissociation equilibria in water will be:

HA + H₂O   ⇄ H₃O⁺ + A⁻    with  Ka = [ H₃O⁺] x [A⁻]/ [HA]

The pH is the negative log of the H₃O⁺ concentration, we know the equilibrium constant, Ka and the original acid concentration. So we will need to find the [H₃O⁺] to solve this question.

In order to do that lets set up the ICE table helper which accounts for the species at equilibrium:

                          HA                                   H₃O⁺                          A⁻          

Initial, M             0.40                                   0                              0

Change , M          -x                                     +x                            +x

Equilibrium, M    0.40 - x                              x                               x

Lets express these concentrations in terms of the equilibrium constant:

Ka = x² / (0.40 - x )

Now the equilibrium constant is so small ( very little dissociation of HA ) that is safe to approximate 0.40 - x to 0.40,

7.3 x 10⁻⁶ = x² / 0.40  ⇒ x = √( 7.3 x 10⁻⁶ x 0.40 ) = 1.71 x 10⁻³

[H₃O⁺] = 1.71 x 10⁻³

Indeed 1.71 x 10⁻³ is small compared to 0.40 (0.4 %). To be a good approximation our value should be less or equal to 5 %.

pH = - log ( 1.71 x 10⁻³ ) = 3.8

Note: when the aprroximation is greater than 5 % we will need to solve the resulting quadratic equation.

4 0
3 years ago
From a 2.875 g sample containing only iron, sand, and salt, 0.660 g of iron and 1.161 g of sand were separated and recovered. Wh
Serjik [45]

Answer:

36.66%

Explanation:

Step 1: Given data

  • Mass of iron: 0.660 g
  • Mass of sand: 1.161 g
  • Mass of the sample: 2.875 g
  • Mass of salt: ?

Step 2: Calculate the mass of salt

The mass of the sample is equal to the sum of the masses of the components.

m(sample) = m(iron) + m(sand) + m(salt)

m(salt) = m(sample) - m(iron) - m(sand)

m(salt) = 2.875 g - 0.660 g - 1.161 g

m(salt) = 1.054 g

Step 3: Calculate the percent of salt in the sample

We will use the following expression.

%(salt) = m(salt) / m(sample) × 100%

%(salt) = 1.054 g / 2.875 g × 100% = 36.66%

7 0
3 years ago
Na+H2O=NaOH+H2<br> Balancing
elena55 [62]

Answer:

Hey mate, here is your answer. Hope it helps you.

Explanation:

The balanced equation is 2Na+2H2O———-> 2NaOH +H2.

6 0
3 years ago
Copper was the first metal to be produced from its ore because it is the easiest to smelt, that is, to refine by heating in the
Ganezh [65]

Answer:

57.48%

Explanation:

Calculate the mass of 1 mole of malachite:

MM Cu = 63.55

MM O = 16.00

MM H = 1.01

MM C = 12.01

(Cu_{2}(OH)_{2}CO_{3})

A mole of malachite has:

2 moles of Cu

5 moles of O

2 moles of H

1 mole of C

MW Malachite = 2*MM(CU) + 5*MM(O) + 2*MM(H) + 1 *MM(C)

MW Malachite = 2*63.55 + 5*16.00 + 2*1.01 + 1*12.01

MW Malachite = 221.13

Mass of Cu in a mole of Malachite = 2*MM(CU) = 127.1

Now divide the mass of Cu by the mass of Malachite

%Cu = \frac{127.1}{221.13} =0.5748=57.48%

7 0
3 years ago
Tips for memorizing the first 20 elements of the periodic table?​
Anna [14]

Answer:

hydrant flying with balloon, balloon has lithp letting air out, bee: really yum balloon

    =                           =                                 =                                   =

hydrogen              helium                     lithium                     beryllium

be bore on the balloon, balloon pops, hydrant drops and makes a car bomb

           =                                                                                                  =

    boron                                                                                              carbon

night row general gets hurt by car bomb nearby, that general gets off boat

        =                                

nitrogen

wearing oxygen mask, mask is full of fluride gel, then he got neon teeth

             =                                               =                                      =

         oxygen                                fluorine                                neon

(try making a story out of the elements, use your imagenation)

7 0
3 years ago
Read 2 more answers
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