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N76 [4]
3 years ago
14

1. Laura uses a cotton swab to collect microorganisms from a hand rail and streaks a plate. On the fourth day of incubation, she

does not observe visible microbial growth. Given that microorganisms are literally everywhere, give at least three reasons why Laura may not have observed microbial growth?
Biology
1 answer:
weeeeeb [17]3 years ago
3 0

Answer:

The Laura tried to grow micro-organisms in culture broth medium in Petri-plates but the microbial growth was not observed even on the fourth day of culture which could be due to:

1. Laura could have not provided the correct broth medium maintaining the with pH and salt concentrations.

2. Microorganisms did not get optimal growth conditions.

3. The bacterial source could have died after the collection which could have lysed after their death and thus no longer visible.

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Since bees and butterflies both pollen are flowers, the growth (population) of flowering plants would become less common without the pollen being spread.
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A normal breath takes in about 1.0 L of air. If air has an average molar mass of 28.8 g per 1 mol and has a density of 0.97 g/mL
Ann [662]

Taking into account the definition of density and Avogadro's Number, you take 2.0286×10²⁵ molecules of air.

<h3>What is density</h3>

Density is defined as the property that matter, whether solid, liquid or gas, has to compress into a given space.

In other words, density is a quantity that allows us to measure the amount of mass in a certain volume of a substance.

Then, the expression for the calculation of density is the quotient between the mass of a body and the volume it occupies:

density=\frac{mass}{volume}

<h3>What is Avogadro's Number</h3>

Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023×10²³ particles per mole. Avogadro's number applies to any substance.

<h3>Amount of molecules of air</h3>

In this case, you know that:

  • Density= 0.97 \frac{g}{mL}
  • Volume= 1 L= 1000 mL

Replacing in the definition of density:

0.97 \frac{g}{mL}=\frac{mass}{1000 mL}

Solving:

mass= 0.97 \frac{g}{mL}  ×1000 mL

<u><em>mass= 970 g</em></u>

Air has an average molar mass of 28.8 g per 1 mol. Then 970 grams are contained in 33.68 moles.

Now, considering the definition of Avogadro's number you can apply the following rule of three: If 1 mole of air contains 6.023×10²³ molecules, 33.68 moles contains how many molecules?

amount of molecules = (33.68 moles× 6.023×10²³ molecules)÷ 1 mole

<u><em>amount of molecules= 2.0286×10²⁵ molecules</em></u>

Finally, you take 2.0286×10²⁵ molecules of air.

Learn more about

density:

brainly.com/question/952755

brainly.com/question/1462554

Avogadro's Number:

brainly.com/question/11907018

brainly.com/question/1445383

brainly.com/question/1528951

#SPJ11

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