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Semenov [28]
3 years ago
14

6. An environmental chemist needs a carbonate buffer of pH 10.00 to study the effects of acid rain on limestone-rich soils. To p

repare this buffer she will add solid Na2CO3 (106.0 g/mol) to 1.50 L of 0.20 M NaHCO3 . (Ka = 4.7 x 10−11 ) HCO3 − (aq) + H2O(l) ↔ CO3 2− (aq) + H3O + (aq) A. What must the final concentration of Na2CO3 be once mixed with the NaHCO3 solution to obtain a buffer with the correct pH?
Chemistry
1 answer:
pishuonlain [190]3 years ago
5 0

Answer:

[Na₂CO₃] = 0.094M

Explanation:

Based on the reaction:

HCO₃⁻(aq) + H₂O(l) ↔ CO₃²⁻(aq) + H₃O⁺(aq)

It is possible to find pH using Henderson-Hasselbalch formula:

pH = pka + log₁₀ [A⁻] / [HA]

Where [A⁻] is concentration of conjugate base,  [CO₃²⁻] = [Na₂CO₃] and  [HA] is concentration of weak acid, [NaHCO₃] = 0.20M.

pH is desire pH and pKa (<em>10.00</em>) is -log pka = -log 4.7x10⁻¹¹ = <em>10.33</em>

<em />

Replacing these values:

10.00 = 10.33 + log₁₀ [Na₂CO₃] / [0.20]

<em> [Na₂CO₃] = 0.094M</em>

<em />

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An oxide of aluminum contains 0.545 g of Al and 0.485 g of O. Find the empirical formula
uysha [10]

Answer:

The answer is: <u>Al2O3</u>

Explanation:

The data they give us is:

  • 0.545 gr Al
  • 0.485 gr O.

To find the empirical formula without knowing the grams of the compound, we find it per mole:

  • 0.545 g Al * 1 mol Al / 27 g Al = 0.02 mol Al
  • 0.485 g O * 1 mol O / 16 g O = 0.03 mol O

Then we must divide the results obtained by the lowest result, which in this case is 0.02:

  • 0.02 mol Al / 0.02 = 1  Al
  • 0.03 mol O / 0.02 = 1.5  O

Since both numbers have to give an integer, multiply by 2 until both remain integers:

  • 1Al * 2 = 2Al
  • 1.5O * 2 = 3O

Now the answer is given correctly:

  • Al2O3

8 0
3 years ago
Using the equations and enthalpy values provided, which mathematical expression can be used to determine the unknown enthalpy ch
vlabodo [156]
In order to solve this, we need to make use of Hess' Law.

We are already given the equations and their corresponding deltaH. Using Hess' Law, we can generate this equation:
104 kJ = x - (-1182 kJ) - (-1144 kJ)

Among the choices, the answer is
<span>B.104 = x - [(-1182) + (-1144)] 
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3 0
3 years ago
Read 2 more answers
8. The time period of artificial satellite in a circular orbit of radius R is T. The radius of the orbit in which time period is
Elena-2011 [213]

Explanation:

It is given that,

The time period of artificial satellite in a circular orbit of radius R is T. The relation between the time period and the radius is given by :

T^2\propto R^3

The radius of the orbit in which time period is 8T is R'. So, the relation is given by :

(\dfrac{T}{T'})^2=(\dfrac{R}{R'})^3

(\dfrac{T}{8T})^2=(\dfrac{R}{R'})^3  

\dfrac{1}{64}=(\dfrac{R}{R'})^3

R'=4\times R

So, the radius of the orbit in which time period is 8T is 4R. Hence, this is the required solution.  

4 0
3 years ago
2Fe(OH)3 Fe2O3+3H2O how many grams of Fe2O3 are produced if 10.7 grams of Fe (OH)3 react in this way
sasho [114]

Answer: 7.98 grams of Fe_2O_3 are produced if 10.7 grams of Fe(OH)_3 are reacted.

Explanation:

To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}      .....(1)  

Putting values in equation 1, we get:

\text{Moles of} Fe(OH)_3=\frac{10.7g}{106.87g/mol}=0.100mol  

The chemical equation for the reaction is

2Fe(OH)_3\rightarrow Fe_2O_3+3H_2O

By Stoichiometry of the reaction:

2 moles of Fe(OH)_3 produce = 1 mole of Fe_2O_3

So, 0.100 moles of Fe(OH)_3 produce= \frac{1}{2}\times 0.100=0.05mol of Fe_2O_3  

Mass of Fe_2O_3 =moles\times {\text{Molar Mass}}=0.05mol\times 159.69g/mol=7.98g  

Hence 7.98 grams of Fe_2O_3 are produced if 10.7 grams of Fe(OH)_3 are reacted.

3 0
2 years ago
What is magma and what does it create? How?
Genrish500 [490]
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5 0
3 years ago
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