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3 years ago

Solve (2 x 10^3) + (7 x 10^5) *

Chemistry

1 answer:

elena-14-01-66 [18.8K]3 years ago

7 0

Scientific Notation:
7.02x10^5
Expanded Form:
702000

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How many grams of sodium benzoate should be added to prepare the buffer? Neglect the small volume change that occurs when the so

expeople1 [14]

Answer:

$2.72$ grams

Explanation:

Complete question is

You are asked to pre pare a pH = 4.00 buffer starting from 1.50 L of 0.0200 M solution of benzoic acid

(C6H5COOH)

and any amount you need of sodium benzoate

(C6H5COONa)

How many grams of sodium benzoate should be added to prepare the buffer? Neglect the small volume change that occurs when the sodium benzoate is added.

Solution

Given

pH of the buffer solution $= 4$

Concentration of C6H5COOH $= 0.02$ M

Volume of the buffer solution $= 1.50$ L

$K_a$ value for benzoic acid is $6.3 * 10^ {-5}$

Concentration of sodium benzoate

$pH = - log Ka + log \frac{C6H5COONa}{C6H5COOH}$

Substituting the given values we get

$log \frac{C6H5COONa}{C6H5COOH} = 4 + log (6.3 * 10^ {-5})\\log \frac{C6H5COONa}{C6H5COOH} = -0.20\\\frac{C6H5COONa}{C6H5COOH} = 10^{-0.2}\\{C6H5COONa} = 10^{-0.2} * 0.02\\{C6H5COONa} = 0.63 * 0.02\\{C6H5COONa} = 0.0126 M$

Number of moles in sodium benzoate

$= 0.0126 * 1.5 \\= 0.0189 Mol$

Mass of sodium benzoate

$0.0189 mol * 144.147 \frac{g}{mol} \\= 2.72 g$

3 0

3 years ago

Which colorless and odorless gas, produced by radioactive decay of Uranium-238, is considered to be a cancer-causing agent?

DiKsa [7]

B, radon is correct. Interestingly, it often collects in basements from radioactive decay of rocks such as granite that contain uranium. Because it is an unreactive noble gas and because it is denser than air it sits in basements and must be pumped out. It collects in human lungs and is the second leading cause of lung cancer behind smoking.

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3 years ago

Consider an ion with the symbol X2+ formed from a representative element. (5.2, 5.3)a. What is the group number of the element?b

sdas [7]

Answer:

a) the element belongs to group 2

b) see image attached

c) Magnesium

d) X3N2

Explanation:

Any ion with the formula X^2+ was derived from group 2 elements. The group two element found in period 3 is magnesium alone.

Since the nitride ion has a valency of -3 and X^2+ has a valency of +2 , then a compound formed between X^2+ and the nitride ion will have the formula X3N2.

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3 years ago

A student is monitoring the pressure of a gas in a rigid container. The amount of gas particles and the volume of the container

GenaCL600 [577]

a.The gas pressure will decrease.

Explanation:

If in a rigid container, the amount of gas particles and volume of the container is held constant, the pressure will decrease if the temperature is reduced.

Gases are highly random particles and they require a high amount of kinetic energy to be in their state of matter.
In a condition where volume of container is fixed, the amount of gas particles is fixed and the temperature reduced, the kinetic energy of the gas particles will directly reduce.
The kinetic energy of gases is directly related to temperature.

Learn more:

kinetic theory brainly.com/question/9924094

#learnwithBrainly

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4 years ago

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Which substance is an electrolyte? 1. O2 2. Xe 3. C3H8 4. KNO3

Troyanec [42]

KNO3 is an electrolyte

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3 years ago