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lukranit [14]
3 years ago
14

You want to determine the protein content in milk with the Kjeldahl method. You take 100 g whole milk and use 100 mL of 0.5 M hy

drochloric acid to collect ammonia. You needed 34.50 mL of 0.3512 M NaOH for the back-titration. Calculate the percentage of protein in the sample?
Chemistry
1 answer:
SCORPION-xisa [38]3 years ago
8 0

Answer:

82.53 % protein in the milk.

Explanation:

<em>Titration formula:</em>

Conc (acid) × Vol (acid) = Conc (base) × Vol (base)

<u>Beginning from back-titration:</u>

0.5 M HCl × Vol  (HCl) = 0.3512 (conc of NaOH) × 34.50 mL (vol of NaOH)

=  \frac{12.1164}{0.5} = 24.2328 mL

⇒ <em>Vol of HCl used in initial titration is 24.2328 mL</em>

So from Initial Titration:

Using same titration formula,

0.5 × 24.2328 = Conc. (base) × 100 ml

Conc (base) = 12.1164 ÷ 100

= 0.121164 M.

But concentration = mass ÷ molar mass

0.121164 = \frac{100 g}{ molar  mass}

= 825.3277 g/mol of protein

⇒ \frac{825.32765}{1000} × 100

= <u>82.53 % protein in the milk.</u>

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How many are molecules ( or formula) in each sample?
andre [41]

Answer:

  • 4.010 \times 10^{25} \text { molecules of } \mathrm{NaHCO}_{3} \text { present in } 55.93 \mathrm{kg} \text { of } \mathrm{NaHCO}_{3}
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<u>Explanation</u>:

<u>Number of molecules for 55.93 \mathrm{kg} \text { of } \mathrm{NaHCO}_{3}</u>

\text { Firstly molar mass is calculated of } \mathrm{NaHCO}_{3}:

Atomic mass of Na + H + C + 3(O)  = 22.99 + 1.008 + 12.01 + 3 × 16.00 = 84.00 g/mol

\text { Number of molecules of } \mathrm{NaHCO}_{3} \text { in } 55.93 \text { kg are as follows: }

55.93 \times\left(10^{3} \mathrm{gm}\right) \times \frac{1 \mathrm{mol} \mathrm{NaHCO}_{3}}{84.00 \mathrm{gm} \mathrm{NaHCO}_{3}} \times\left(6.022 \times 10^{23} \mathrm{molecules} \text { i.e Avogadro number }\right)

=4.010 \times 10^{26} \text { molecules of } \mathrm{NaHCO}_{3} \text { present in } 55.93 \mathrm{kg} \text { of } \mathrm{NaHCO}_{3}

<u>Number of molecules for for \left(4.59 \times 10^{5} \mathrm{gm}\right) \text { of } \mathrm{Na}_{3} \mathrm{PO}_{4}</u>

\text { Firstly molar mass is calculated of } \mathrm{Na}_{3} \mathrm{PO}_{4}

= Atomic mass of 3(Na) + P + 4(O)

= 3(22.99) + 30.97 + 4(16.00) = 163.94 g/mol

459 \times\left(10^{3} \mathrm{gm}\right) \times \frac{1 \mathrm{mol} N a_{3} P O_{4}}{163.94 \mathrm{gm} N a_{3} P O_{4}} \times\left(6.022 \times 10^{23} \mathrm{molecules} \text { i.e Avogadro number) } / 1 \mathrm{mol}\right.

=16.86 \times 10^{26} \text { molecules of } \mathrm{Na}_{3} \mathrm{PO}_{4} \text { present in } 459 \mathrm{kg}\left(4.59 \times 10^{5} \mathrm{gm}\right) \text { of } \mathrm{Na}_{3} \mathrm{PO}_{4}

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3 years ago
When energy in the atom is released, what occurs?
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What happens when electrons in atoms absorb or release energy? When electrons absorb or release energy, their electrons can move to higher or lower energy levels. These electrons lose energy by emitting light when they return to lower energy levels.

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i really hope this helps

4 0
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Help ASAP pleaseeee thank you
Artyom0805 [142]
The correct answer is B. balance
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