What is the section of lithosphere that carries crust

16.78 A buffer is prepared by mixing 525 mL of 0.50 M formic acid, HCHO2, and 475 mL of 0.50 M sodium for- mate, NaCHO2. Calcula

dolphi86 [110]

Answer: Before addition of HCl, the pH is 3.70 and after addition of HCl, the pH is 3.64 .

Explanation: The pH of the buffer solution is calculated by using Handerson equation:

$pH=pKa+log(\frac{base}{acid})$

Let's calculate the moles of acid and base(salt) present in the original buffer.

mL are converted to L and then multiplied by molarity to get the moles.

$525mL(\frac{1L}{1000mL})(\frac{0.50molHCHO_2}{1L})$

= $0.2625molHCHO_2$

$475mL(\frac{1L}{1000mL})(\frac{0.50molNaCHO_2}{1L})$

= $0.2375molNaCHO_2$

Total volume of the buffer solution = 0.525 L + 0.475 L = 1.00 L

Since, the total volume is 1.00 L, concentration of base will be 0.2375 M and the concentration of acid will be 0.2625 M.

pKa for formic acid is 3.74. Let's plug in the values in the equation and calculate the pH of the original buffer.

$pH=3.74+log(\frac{0.2375}{0.2625})$

pH = 3.74 - 0.04

pH = 3.70

Now, we add 8.6 mL of 0.15 M HCl acid to 85 mL of the buffer. Let's calculate the moles of acid and base in 85 mL of the buffer.

$85mL(\frac{1L}{1000mL})(\frac{0.2625molHCHO_2}{1L})$

= $0.0223molHCHO_2$

$85mL(\frac{1L}{1000mL})(\frac{0.2375molNaCHO_2}{1L})$

= $0.0202molNaCHO_2$

Now, let's calculate the moles of HCl added to the buffer.

$8.6mL(\frac{1L}{1000mL})(\frac{0.15molHCl}{1L})$

= 0.00129 mol HCl

This added HCl reacts with base(sodium formate) and formic acid is produced.

So, 0.00129 moles of HCl will react with 0.00129 moles of sodium formate to produce 0.00129 moles of formic acid. We can write formate ion in place of sodium formate and hydrogen ion in place of HCl. The equation would be:

$H^++CHO_2^-\rightarrow HCHO_2$

moles of base after reaction with HCl = 0.0202 mol - 0.00129 mol = 0.01891 mol

moles of acid after addition of HCl = 0.0223 mol + 0.00129 mol = 0.02359 mol

Let's plug in the values again in the Handerson equation and calculate the pH:

$pH=3.74+log(\frac{0.01891}{0.02359})$

pH = 3.74 - 0.096

pH = 3.64

8 0

3 years ago

How many moles are in 0.0723 atoms of Iron. Fe?-

Vlada [557]

Answer:

0.012× 10⁻²³ moles of iron

Explanation:

Given data:

Number of moles of iron = ?

Number of iron atoms = 0.0723 atom

Solution:

Avogadro number:

It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance. The number 6.022 × 10²³ is called Avogadro number.

1 mole = 6.022 × 10²³ atoms

0.0723 atom × 1 mol / 6.022 × 10²³ atoms

0.012× 10⁻²³ mol

8 0

3 years ago

Yvonne is interested in the field which weighs morality and the technological ability to modify genetic material in humans. She

kodGreya [7K]

Hello there! It sounds like she intends to pursue a career in Genetic engineering

Genetic engineering is "the deliberate modification of the characteristics of an organism by manipulating its genetic material". Since Yvonne is interested in the possibility of modifying human DNA, this seems to be the perfect fit since it involves modifying DNA.

Hope this helps, have a great day!

3 0

3 years ago

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Any reaction that absorbs 150 kcal of energy can be classified as

Dennis_Churaev [7]

The answer should be (D) endothermic reaction.

Reason : - Reactions in which energy is absorbed are called endothermic reactions. In your provided question, 150 kcal energy is being <u>absorbed</u>, and thus, we can say that it is an endothermic reaction.

6 0

3 years ago

Which of the following processes would you predict to have an increase in entropy?

arlik [135]

Among the choices given, the best answer is the third option. Melting ice shows an increase in entropy. Entropy is the degree of disorderliness in a system. Among the phases, solid has the most ordered structure which means it has the least entropy. The ice melting shows a phase change from solid to liquid. Liquid molecules are more disorganized than the solid thus there is an increase in entropy.

3 0

3 years ago

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