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insens350 [35]
3 years ago
11

A chemist must prepare 0.9 L of sodium hydroxide solution with a pH of 13.40 at 25°C. He will do this in three steps: Fill a 0.9

L volumetric flask about halfway with distilled water. Weigh out a small amount of solid sodium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of sodium hydroxide that the chemist must weigh out in the second step.
Chemistry
1 answer:
oksano4ka [1.4K]3 years ago
4 0

Answer:

9.04 g

Explanation:

Given that:

pH of NaOH = 13.40

pOH = 14 - pH

pOH = 14 - 13.40

pOH = 0.6

Now, from there we can find the concentration of NaOH = [OH⁻]

= 10^{-pOH}

= 10^{-0.6}

= 0.2512 M

Given that; volume = 0.9 L

∴ number of moles of NaOH = volume × concentration of NaOH

= 0.9 × 0.2512

= 0.2261 moles

mass of NaOH = number of moles of NaOH × molar mass of  NaOH

mass of NaOH = 0.2261  × 40

mass of NaOH = 9.04 g

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zavuch27 [327]
The best way to accurately determine the pair with the highest electronegativity difference is by using their corresponding electronegativity values. For the each of the choices, the difference is:

A. H-S = 2.5 - 2.1 = 0.4
B. H-Cl = 3 - 2.1 = 0.9
C. N-H = 3 - 2.1 = 0.9
D. O-H = 3.5 - 2.1 = 1.4
E. C-H = 2.5 - 2.1 = 0.4

As show, D. has the highest difference. Without looking at their values, you can also determine the pair with the highest difference by taking note of the trend of electronegativity on the periodic table. Electronegativity increases as you go right a group and up a period. This makes oxygen the most electronegative element among the other elements paired with hydrogen.
4 0
3 years ago
Which of the following is false? a. an apoenzyme can catalyze its reaction without its cofactor b an organic cofactor can be cal
ozzi

Answer: Option (a) is the correct answer.

Explanation:

A protein part of an enzyme is known as an apoenzyme. An apoenzyme combines with a cofactor, it is known as holoenzyme.

Without a cofactor an apoenzyme cannot function as cofactor helps in the formation of an active enzyme system and provides a specific site on enzyme for the substrate.

Whereas a non-protein chemical compound or metal ion that helps in the activity of enzyme as a catalyst is known as a cofactor. A metal ion cofactor can be bound directly to the enzyme or to a coenzyme.

The organic non-protein molecules which bind to the protein molecule to form an active enzyme is known as a coenzyme. Coenzymes are small size molecules which help the enzymes to act as a catalyst.

Therefore, we can conclude that the statement an apoenzyme can catalyze its reaction without its cofactor, is false.

3 0
4 years ago
La densidad del óxido de magnesio. MgO, es de 3.581 g/cm3 El MgO, es de 3.581 g/cm3 El MgO cristaliza con ordenamiento cúbico co
Jobisdone [24]

Answer:

a=4.213cm

r=1.490x10^{-8}cm

Explanation:

Hola.

En este caso, para calcular la longitud (a) de una cara de celda unitaria, consideramos la siguiente ecuación:

\rho =\frac{#at*M}{a^3N_A}

En la que consideramos el número de átomos por celda (4 para FCC), la masa molar (40.3 g/mol para MgO) y el número de avogadro para obtener:

3.581g/mol = \frac{4atom/celda*40.3g/mol}{a^3*6.02x10^{23}atom/mol}

Despejando para a, obtenemos:

a^3 = \frac{4atom/celda*40.3g/mol}{3.581g/cm^3*6.02x10^{23}atom/mol}\\\\a=\sqrt[3]{7.478cm^3} \\\\a=4.213cm

Finalmente, el radio lo calculamos como:

r=\frac{\sqrt{2}*a}{4}=\frac{\sqrt{2}*4.213x10^{-8}cm}{4}\\\\r=1.490x10^{-8}cm

¡Saludos!

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3 years ago
Gold is used for jewelry because it is malleable. This means it can be easily molded into different shapes. What is this an exam
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Malleablity is a physical property so hence

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3 years ago
Which statements correctly describe the process of nuclear fusion?
Keith_Richards [23]

It bonds atoms together to create molecules

4 0
3 years ago
Read 2 more answers
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