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3 years ago

Which of the following describes an element? Choose all that apply.

Chemistry

1 answer:

Kisachek [45]3 years ago

5 0

Answer:

A) Gold is an example.

D) There is only one type of substance present.

F) Composed of one type of atom with its own unique properties.

Explanation:

Hello! These are the correct answers! (I took the K12 quiz)

Have a blessed day! :)

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Answer:

The second one is the answer

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What do hydroelectric plants use to turn a turbine when producing electrical energy?

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A. water
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3 years ago

Does Catalysts increase the rate of chemical reactions. true or false

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True.

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3 years ago

Calculate the pKa of lactic acid (CH3CH(OH)COOH) given the following information. 3.005 grams of potassium lactate are added to

snow_lady [41]

Answer:

$\displaystyle \text{p} K_a \approx 3.856$

Explanation:

Because 3.005 grams of potassium lactate is added to 100. mL of solution, its concentration is:

$\displaystyle \begin{aligned} \left[ \text{KC$_3$H_$_5$O$_3$}\right] & = \frac{3.005\text{ g KC$_3$H_$_5$O$_3$}}{100.\text{ mL}} \cdot \frac{1\text{ mol KC$_3$H_$_5$O$_3$}}{128.17 \text{ g KC$_3$H_$_5$O$_3$}} \cdot \frac{1000\text{ mL}}{1\text{ L}} \\ \\ &= 0.234\text{ M}\end{aligned}$

By solubility rules, potassium is completely soluble, so the compound will dissociate completely into potassium and lactate ions. Therefore, [KC₃H₅O₃] = [C₃H₅O₃⁺]. Note that lactate is the conjugate base of lactic acid.

Recall the Henderson-Hasselbalch equation:

$\displaystyle \begin{aligned}\text{pH} = \text{p}K_a + \log \frac{\left[\text{Base}\right]}{\left[\text{Acid}\right]} \end{aligned}$

[Base] = 0.234 M and [Acid] = 0.500 M. We are given that the resulting pH is 3.526. Substitute and solve for p<em>Kₐ</em>:

$\displaystyle \begin{aligned} (3.526) & = \text{p}K_a + \log \frac{(0.234)}{(0.500)} \\ \\ 3.526 & = \text{p}K_a + (-0.330) \\ \\ \text{p}K_a & = 3.856\end{aligned}$

In conclusion, the p<em>Kₐ </em>value of lactic acid is about 3.856.

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2 years ago

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Ilya [14]

Answer:

Explanation:

Oil or Lipid + Base lead to Glycerol and Soap

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3 years ago

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