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bija089 [108]
3 years ago
12

A chemist makes 620 mL of barium chloride working solution by adding distilled water to180mL of a 1.39mol/L stock solution of ba

rium chloride in water. Calculate the concentration of the chemist's working solution. Be sure your answer has the correct number of significant digits.
Chemistry
2 answers:
katen-ka-za [31]3 years ago
7 0

Answer:

The correct answer is 0.40 mol/L.

Explanation:

In order to solve the problem, we use the following expression, where V1 and C1 are the volume and concentration of stock solution and V2 and C2 are the volume and concentration of working solution:

V1 x C1= V2 x C2

⇒C2= V1 x C1/ v2

  C2= (180 ml x 1.39 mol/L)/ 620 ml

  C2= 0.40 mol/L

Svetllana [295]3 years ago
6 0

Answer:

0.404 mol / L

Explanation:

The <em>total moles of barium chloride</em> can be calculated from <em>the volume and concentration of the stock solution</em>:

1.39 mol/L * 0.180 L = 0.2502 moles barium chloride

Now we <u>calculate the concentration of the working solution, by dividing the total moles by the final volume</u>:

0.2502 mol / 0.620 L = 0.404 mol / L

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½H2(g) + ½I2(g) → HI(g), ΔH = +6.2 kcal/mole 21.0 kcal/mole + C(s) + 2S(s) → CS2(l) What type of reaction is represented by the
wlad13 [49]

<u>Answer:</u>

Exothermic Reaction are those reaction, in which energy is released while in endothermic reaction are those, in which energy is absorbed.

<u>Explanation:</u>

First Reaction:

As in this reaction, energy is released

½H2(g) + ½I2(g) → HI(g), ΔH = +6.2 kcal/mole

so it is <em>exothermic reaction</em>

Second reaction:

As in this reaction, energy is absorbed

21.0 kcal/mole + C(s) + 2S(s) → CS2(l)

so it is <em>endothermic reactions</em>.


7 0
4 years ago
Read 2 more answers
If a system performs 147 kJ of work while receiving 47 kJ of heat, what is change in its internal energy?
Verdich [7]

Answer:

-100 kJ

Explanation:

We can solve this problem by applying the first law of thermodynamics, which states that:

\Delta U = Q-W

where:

\Delta U is the change in internal energy of a system

Q is the heat absorbed/released by the system (it is positive if absorbed by the system, negative if released by the system)

W is the work done by the system (it is positive if done by the system, negative if done on the system)

For the system in this problem we have:

W = +147 kJ is the work done by the system

Q = +47 kJ is the heat absorbed by the system

So , its change in internal energy is:

\Delta U = +47 - (+147) =-100 kJ

6 0
3 years ago
What do you think might be different between fat molecules and carbohydrate and protein molecules?
dimulka [17.4K]

Answer:

Long answer

Proteins are the building blocks of the body, each and every organ muscle and skin and cells are made of proteins. They can also be used for providing energy to the body in a state where other energy sources aren't available.

Fats are stored energy blocks which can be used by the body at its own convenience whenever there is a deficit of energy in the body. They can also be directly burnt to give energy in cases where energy needs of the body are not met by dietary intake

Carbohydrates are the most convenient and preferable source of energy in the body and are easily converted to give out immidiate energy to the body, excess carbohydrates can be converted into fats and stored for later usage as and when required by the body.

Proteins, fats and carbohydrates have many secondary functions and roles in the human body. If you are keen to know anything more specific feel free to ask.

<h3>Short answer :</h3>

Fats are used for energy after they are broken into fatty acids. Protein can also be used for energy, but the first job is to help with making hormones, muscle, and other proteins.

7 0
2 years ago
Read 2 more answers
A chemist dissolves 867. mg of pure barium hydroxide in enough water to make up 170. mL of solution. Calculate the pH of the sol
Ilya [14]

Answer: The pH of the solution is 11.2

Explanation:

Molarity of a solution is defined as the number of moles of solute dissolved per liter of the solution.

Molarity=\frac{n\times 1000}{V_s}

where,

n = moles of solute

V_s = volume of solution in ml

moles of Ba(OH)_2 = \frac{\text {given mass}}{\text {Molar mass}}=\frac{0.867g}{171g/mol}=0.00507mol         (1g=1000mg)

Now put all the given values in the formula of molality, we get

Molarity=\frac{0.00507\times 1000}{170}

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pH or pOH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydrogen ion concentration.

pOH=-\log [OH^-]

Ba(OH)_2\rightarrow Ba^{2+}+2OH^{-}

According to stoichiometry,

1 mole of Ba(OH)_2 gives 2 mole of OH^-

Thus 0.0298 moles of Ba(OH)_2 gives =\frac{2}{1}\times 0.0298=0.0596 moles of OH^-

Putting in the values:

pOH=-\log[0.0596]=2.82

pH+pOH=14

pH=14-2.82

pH=11.2

Thus the pH of the solution is 11.2

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Is water going from liquid to solid a physical or chemical change and why
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It would be a physical change. It’s still water just in a different physical form. If it was a chemical change, it would no longer be water. For example, when the ice melts back into water...it’s still water.
6 0
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