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Olin [163]
3 years ago
11

Suppose you want to test the results of a transformation by growing Escherichia coli cells in LB medium containing ampicillin as

the antibiotic for selection. Ampicillin at a concentration of 100 µg/mL will kill cells that do not contain an ampicillin resistance gene, but will allow the growth of cells that have been transformed with this gene. The concentrated stock of ampicillin is 100 mg/mL. How many microliters of the ampicillin stock should you add to 50 mL of LB for a bacterial culture?
Chemistry
1 answer:
mestny [16]3 years ago
7 0

Answer:

50.0 μL

Explanation:

When a dilution is done, the mass of the solute (in this case the ampicillin) remains constant, following the Lavoiser's law that the mass is conserved. The mass is the concentration (C) multiplied by the volume (V), so if 1 is the stock solution, and 2 is the bacterial culture after the addition of the antibiotic:

m1 = m2

C1*V1 = C2*V2

C1 = 100 mg/mL = 100000 μg/mL (1 mg = 1,000μg)

C2 = 100 μg/mL

V2 = 50 mL + V1 = 50000μL + V1 (V1 in μL)

100000*V1 = 100*(50000 + V1)

1000V1 = 50000 + V1

999V1 = 50000

V1 = 50.0 μL

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In a coffee-cup calorimeter, 50.0ml of 0.100M AgNO3 and50.0ml of 0.100M HCl are mixed to yield the following reaction:
Marina CMI [18]

Answer:

-66.88KJ/mol

Explanation:

It is possible to obtain the heat involved in a reaction using a calorimeter. Formula is:

q = -C×m×ΔT

<em>Where q is heat of reaction, C is specific heat capacity (4.18J/°Cg), m is mass of solution (100.0g) and ΔT is temperature change (23.40°C-22.60°C = 0.80°C)</em>

Replacing:

q = -4.18J/°Cg×100.0g×0.80°C

q = -334.4J

Now, in the reaction:

Ag⁺ + Cl⁻→ AgCl

<em>AgNO₃ as source of Ag⁺ and HCl as source of Cl⁻</em>

Moles that react are:

0.050L× (0.100mol /L) = 0.0050moles

If 0.0050 moles produce -334.4J. Heat of reaction is:

-334.4J / 0.0050moles = -66880J/mol = <em>-66.88KJ/mol</em>

5 0
3 years ago
1. As the temperature of the gas in a balloon decreases, which of the following occurs? The volume of the balloon increases. ***
timama [110]
Answer 1:
Correct Answer: T<span>he average kinetic energy of the gas decreases.
</span>Reason: 
From the ideal gas equation, we know that PV = nRT
where, P = pressure, V = volume, n = number of moles of gas, R = gas constant and T = temperature.

From above equation, it can be seen that, Temp. as a direct relation with Pressure and Volume. Hence, as temperature of the gas in a balloon decreases, pressure and volume also decreases. 

Also, from kinetic theory of gases, we know that, kinetic energy of gas increases with increasing temp. Hence,  average kinetic energy of the gas decreases with decreasing temp.  

Answer 2: 
Correct answer: Out
Reason: 
From the ideal gas equation, we know that PV = nRT
where, P = pressure, V = volume, n = number of moles of gas, R = gas constant and T = temperature.

Therefore, when a sealed syringe is heated, it's temp. will increase. This, will result in expansion of gas i.e volume will increase. Hence, <span>syringe plunger move in outwards direction.

Answer 3: Volume = 6046 L
Reason: 
</span>From the ideal gas equation, we know that PV = RT
where, P = pressure, V = volume, R = gas constant and T = temperature.<span>
Given: P1 = 99 kPa, V1 = 3000 L, T1 = 312 K, P2 = 45.5 KPa and  T2 = 289 K.

Therefore, we have: </span>\frac{\text{P1 V1}}{\text{P2 V2}} =  \frac{\text{R T1}}{\text{R T2}}
Thus, \frac{\text{99 3000}}{\text{45.5 V2}} = \frac{\text{R 312}}{\text{R 289}}

Hence, V2 = 6046 L

Answer 4: 
Correct Answer: It increases
Reason: 
We know that, pressure of gas, it directly proportional to temp. Hence, when the temp. of as is increases. Total pressure of gas mixture increases. This is because, partial pressure of individual component (in present case oxygen) increases.

Answer 5: 
Correct answer: 18.5 kPa
Reason:
We know that, total pressure is the sum of the partial pressures of the gases present in it. Mathematically, it can be expressed as:

                           Ptot = PO2 + PHe + PCO2

Therefore,  partial pressure of oxygen, <span>PO2:</span>

                         PO2 = Ptot − PHe − PCO2

                                = 101.4 − 82.5 − 0.4

                                =18.5 kPa.


Answer 6: 

Correct Answer: Argon

Reason: 

<span>Inert gases are the best choice for inflating a balloon that must remain inflated for a long period of time. Among given options, both neon and argon are inert gas, But, atomic weight of Ar is 40g/mol, while is more than that of neon (20 g/mol). Hence,. Argon gas is preferred over neon gas. </span>
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3 years ago
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The pressure of a fixed mass of gas is increased from 100 kPa to 600 kPa at a constant temperature. The new volume of the gas is
Dima020 [189]

Answer: The new volume of the gas is smaller.

Explanation:

Volume and pressure are inversely proportional (as one goes up, one goes down). So as you increase the pressure, you decrease the volume.

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3 years ago
Which statement correctly describes the differences between positive and negative acceleration?
Serga [27]

C. Positive acceleration describes an increase in speed; negative acceleration describes a decrease in speed. ( I put A & it was not the correct answer, the answer was C )

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4 years ago
4. How is a lead storage battery recharged?
alekssr [168]
The answer is c Yep Allll day
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