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weqwewe [10]
3 years ago
13

When must scientist conduct controlled experiments ?

Chemistry
1 answer:
iVinArrow [24]3 years ago
8 0
Usually when scientist wants to test whether one compound or one phenotype is related to another phenotype. Then they need to control this variable when conducting experiments.
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A sample of hydrogen was collected by water displacement at 23.0°C and an atmospheric pressure of 735 mmHg. Its volume is 568 mL
ziro4ka [17]

Answer:

V = 552 mL or 0.552 L

Explanation:

First, we need to calculate the number of moles of H2 using the ideal gas equation which is:

PV = nRT

Solving for n:

n = PV / RT

Where:

P = Pressure

V = Volume

R = Gas constant (0.082 L atm / K mol)

T = Temperature in K

Let's convert first both pressure in atm, remember that 1 atm = 760 mmHg

P = 735 / 760 = 0.967 atm

Pwater = 21 / 760 = 0.028 atm

Finally temperature to Kelvin:

T = 23 + 273.15 = 296.15 K

Now, at first the hydrogen was collected by water displacement so pressure is:

P = 0.967 - 0.028 = 0.939 atm

Now the moles of hydrogen:

n = 0.939 * 0.568 / 0.082 * 296.15

n = 0.022 moles

Now that we have the moles, let's calculate the volume when the pressure is 735 mmHg

V = nRT/P

V = 0.022 * 0.082 * 296.15 / 0.967

V = 0.552 L or 552 mL

This is the volume that hydrogen occupies.

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