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Andreas93 [3]
2 years ago
8

You are asked to make 500 mL of a 0. 250 M sodium chloride (NaCl) solution.

Chemistry
1 answer:
nignag [31]2 years ago
3 0

Answer:

a. .125 mol b. 7.25g

Explanation:

a. To get the moles multiply the volume by the molarity.

.5L*.25M=.125mol NaCl

b. The molar mass is provided so multiply the moles by the molar mass to get the amount of grams of nacl.

.125mol*58molar mass=7.25g nacl to make the solution

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The electron in a hydrogen atom, originally in level n = 8, undergoes a transition to a lower level by emitting a photon of wave
timofeeve [1]

Explanation:

It is given that,

The electron in a hydrogen atom, originally in level n = 8, undergoes a transition to a lower level by emitting a photon of wavelength 3745 nm. It means that,

n_i=8

\lambda=3745\ nm

The amount of energy change during the transition is given by :

\Delta E=R_H[\dfrac{1}{n_f^2}-\dfrac{1}{n_i^2}]

And

\dfrac{hc}{\lambda}=R_H[\dfrac{1}{n_f^2}-\dfrac{1}{n_i^2}]

Plugging all the values we get :

\dfrac{6.63\times 10^{-34}\times 3\times 10^8}{3745\times 10^{-9}}=2.179\times 10^{-18}[\dfrac{1}{n_f^2}-\dfrac{1}{8^2}]\\\\\dfrac{5.31\times 10^{-20}}{2.179\times 10^{-18}}=[\dfrac{1}{n_f^2}-\dfrac{1}{8^2}]\\\\0.0243=[\dfrac{1}{n_f^2}-\dfrac{1}{64}]\\\\0.0243+\dfrac{1}{64}=\dfrac{1}{n_f^2}\\\\0.039925=\dfrac{1}{n_f^2}\\\\n_f^2=25\\\\n_f=5

So, the final level of the electron is 5.

4 0
3 years ago
10. A 2.36-gram sample of NaHCO3 was completely decomposed in an
Airida [17]

Answer:

0.79 g

Explanation:

Let's introduce a strategy needed to solve any similar problem like this:

  • Apply the mass conservation law (assuming that this reaction goes 100 % to completion): the total mass of the reactants should be equal to the total mass of the products.

Based on the mass conservation law, we need to identify the reactants first. Our only reactant is sodium bicarbonate, so the total mass of the reactants is:

m_r=m_{NaHCO_3}=2.36 g

We have two products formed, sodium carbonate and carbonic acid. This implies that the total mass of the products is:

m_p=m_{Na_2CO_3}+m_{H_2CO_3}

Apply the law of mass conservation:

m_r=m_p

Substitute the given variables:

m_{NaHCO_3}=m_{Na_2CO_3}+m_{H_2CO_3}

Rearrange for the mass of carbonic acid:

m_{H_2CO_3}=m_{NaHCO_3}-m_{Na_2CO_3}=2.36 g - 1.57 g=0.79 g

8 0
3 years ago
450 nanometers to meters
lys-0071 [83]

Answer: 4.5 x 10e-7

Explanation: 450 x 1e+9 = correct answer

Multiply amount of nanometers by 1e+9 to get the approximate result in meters.

4 0
3 years ago
a fraction collected during distillation ethanol-water what is the mass of ethanol that is present in this fraction
AURORKA [14]

Answer:

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Explanation:

because the liquid with high boiling point is going to be collected the first

4 0
2 years ago
1. The speed limit on most city streets is (25 miles). How many meters per minute
irina1246 [14]

Answer:

Speed = 670.56 \frac{m}{min}

Explanation:

Given

Speed = \frac{25 mi}{hr}

Required

Convert to meters per minutes

Speed = \frac{25 mi}{hr}

Start by converting the speed from miles to meters

1\ mile = 1609.34\ meters.

So, we have:

Speed = \frac{25 * 1609.34\ m}{hr}

Speed = \frac{40233.5\ m}{hr}

Next, we convert time from hours to minutes

1\ hour = 60\ minutes

So, we have:

Speed = \frac{40233.5\ m}{60\ min}

Speed = 670.56 \frac{m}{min}

<em>Hence, the equivalent of 25 miles per hour is 670.56 meters per minutes</em>

3 0
3 years ago
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