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2 years ago

Which of the following is most helpful when identifying organism using a dichotomous key?

Chemistry

1 answer:

Anastaziya [24]2 years ago

3 0

Answer:

C. Its physical structures

Explanation:

A dichotomous key is defined as a tool used to differentiate between objects and organisms. A dichotomous key consist of series of question related to the species and at the end gives the scientific name of the species.

The characteristic that is most helpful when identifying organism using a dichotomous key is "Its physical structures". for example: if a person want to identify a tree, a dichotomous key ask about the physical structures such as if the tree has needles or leaves.

So, physical structures are most helpful while using a dichotomous key.

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Dilution question In many of the experiments, you will be asked to prepare a standard solution by diluting a stock solution. You

riadik2000 [5.3K]

Answer:

We could do two 1:50 dilutions and one 1:4 dilutions.

Explanation:

Hi there!

A solution that is 1000 ug/ ml (or 1000 mg / l) is 1000 ppm.

Knowing that 1 ppm = 1000 ppb, 100 ppb is 0.1 ppm.

Then, we have to dilute the stock solution (1000 ppm / 0.1 ppm) 10000 times.

We could do two 1:50 dilutions and one 1:4 dilutions (50 · 50 · 4 = 10000). Since the first dilution is 1:50, you will use the smallest quantity of the stock solution (if we use the 10.00 ml flask):

First step (1:50 dilution):

Take 0.2 ml of the stock solution using the third dispenser (20 - 200 ul), and pour it in the 10.00 ml flask. Fill with water to the mark (concentration : 1000 ppm / 50 = 20 ppm).

Step 2 (1:50 dilution):

Take 0.2 ml of the solution made in step 1 and pour it in another 10.00 ml flask. Fill with water to the mark. Concentration 20 ppm/ 50 = 0.4 ppm)

Step 3 (1:4 dilution):

Take 2.5 ml of the solution made in step 3 (using the first dispenser 1 - 5 ml) and pour it in a 10.00 ml flask. Fill with water to the mark. Concentration 0.4 ppm / 4 = 0.1 ppm = 100 ppb.

6 0

3 years ago

His transmitter is mostly located in diffuse neuronal systems in the CNS, with cell bodies particularly in the raphe nuclei. It

joja [24]

Answer: The correct answer is a) Acetylcholine.

Explanation:

The acetylcholine is a very important neurotransmitter involved in the mediation of synaptic activity between neurons. Among its most important functions we find: expression of mood states, vasodilation, gastrointestinal motility, bronchoconstriction, circular iris muscle contraction and sweat gland secretion.

Therefore the correct answer is a) Acetylcholine.

8 0

3 years ago

What is the molarity of a solution containing 56 grams of solute in 959 ml of solution? (molar mass of solute = 26 g/mol)?

jolli1 [7]

26g --- 1 mol
56g --- X
X= 56/26 = 2,154 mol

959 ml = 959cm³ = 0,959dm³

C = n/V
C = 2,154/0,959
C = 2,246 mol/dm³

8 0

3 years ago

Read 2 more answers

What is the ph of a 0.15 m solution of ammonium chloride?

Thepotemich [5.8K]

Best Answer: <span>(a)
8.9 x 10^-7 = x^2 / 0.15-x
x = [OH-] = 0.00037 M
pOH = 3.4
pH = 14 - 3.4 = 10.6

(b)
Ka = Kw/Kb = 5.6 x 10^-10 = x^2 / 0.20-x
x = [H+] = 0.000011 M
pH = 5.0</span>

7 0

3 years ago

The compound cisplatin has been extensively studied as an antitumor agent. It is synthesized by the following, unbalanced reacti

zimovet [89]

The balanced chemical equation would be as follows:

<span>K2PtCl4(aq) + 2NH3(aq) --> Pt(NH3)2Cl2(s) + 2KCl(aq)

We are given the amount of </span>K2PtCl4 to be used in the reaction. This will be the starting point for our calculations. We do as follows:

65 g K2PtCl4 ( 1 mol / 415.09 g ) ( 1 mol Pt(NH3)2Cl2 / 1 mol K2PtCl ) ( 300.051 g / 1 mol ) = 46.99 g Pt(NH3)2Cl produced

6 0

3 years ago

Read 2 more answers