To prepare a buffer you weigh out 7.20 grams of NaHCO3 and place it into a 400.00 mL volumetric flask. To this flask you add 56.0 mL of 5.60 M H2CO3 and then fill it about halfway with distilled water, swirling to dissolve the contents. Finally, the flask is filled the rest of the way to the mark with distilled water. What is the pH of the buffer that you have created?Acid KaH2CO3 4.3 X 10⁻⁷ HCN 4.9 X 10⁻¹⁰HNO2 4.6 X 10⁻⁴C6H5COOH 6.5 X 10⁻⁵

pH = 5.80

Explanation:

The buffer solution is:

H₂CO₃(aq) + H₂O(l) ⇄ HCO₃⁻Na⁺(aq) + H₃O⁺(aq)

To find the pH of the buffer solution we will use the Henderson-Hasselbalch equation:

   (1)

First, we need to find the concentration of the buffer solution. For the NaHCO₃ we have:

Where:

m: is the mass of the NaHCO₃ = 7.20 g

M: is the molar mass of the NaHCO₃ = 84.007 g/mol

V: is the volume of the solution = 400.0 mL

Hence, the concentration of NaHCO₃ is:

Now, the concentration of H₂CO₃ is:

Where:

Vi: is the initial volume of H₂CO₃ = 56.0 mL

Ci: is the initial concentration of H₂CO₃ = 5.60 M

Vf: is the final volume of H₂CO₃ = 400.0 mL

Cf: is the final concentration of H₂CO₃ (to find)

Finally, we can use the equation (1) to find the pH of the buffer solution:

I hope it helps you!

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

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