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3 years ago

A. Stamens (p) The portion of the pistil receiving the pollen

Chemistry

2 answers:

Alja [10]3 years ago

6 0

Answer:

(A) A-(S) ; B-(R) ; C-(Q) ; D-(P).

Explanation:

(A)-S_ The male part of a flower.

(B)-R _The stalk of an anther.

(C)-Q_ The female structure of a flower.

(D)-P _The portion of the pistil recieving the pollen.

Shalnov [3]3 years ago

5 0

I believe the correct answer is B

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Reaction of 0.028 g of magnesium with excess hydrochloric acid generated 31.0 mL of hydrogen gas. The gas was collected by water

MA_775_DIABLO [31]

Explanation:

(a) It is given that magnesium is reacted with hydrochloric acid and the hydrogen evolved is collected at top. This means that hydrochloric acid will be present in a solution (HCl + Water) and the solvent will be water.

Due to evaporation some amount of water will have evaporated and would be present in vapor phase. Therefore, when the reaction occurs only hydrogen will not be present in vapor phase but, will be accompanied by water vapors as well .

Hence, Dalton's law the total pressure of the system will be sum of pressure exerted by hydrogen gas and pressure exerted by water vapors .

Let us assume that the partial pressure of hydrogen gas be " $P_H_{2}$ "

And, the partial pressure of water will be nothing but the vapor pressure of water,

Vapor pressure of water = $P_{water}$

= 19.8 mm Hg

Total pressure of the system = 746 mm Hg

Total pressure = $P_H_{2} + P_{water}$

746 = $P_H_{2}$ + 19.8

or, $P_H_{2}$ = 746-19.8

= 726.2 mm Hg

Hence, partial pressure of hydrogen gas is 726.2 mm Hg.

(b) To calculate volume at STP, we will first calculate at $22^{o}C$ and 726.2 mm Hg and than convert it to STP conditions.

Therefore, to calculate volume at $22^{o}C$ and 726.2 mm Hg we will make use of ideal gas law as follows.

P = 726.2 mm Hg

= $\frac{726.2}{760}$

= 0.955 atm

T = $22^{o}C$

= 22+273.15 = 295.15 K

V = 31 ml = $31 \times 10^{-3}$ Litre

According to the ideal gas law ,

PV = nRT

where, P = pressure of the system ,

V = volume of the gas

N = number of moles

R = 0.0821 liter atm/mole K

T = Temperature

Hence, putting the given values into the above formula as follows.

$0.955 \times 31 \times 10^{-3} = N \times 0.0821 \times 295.15$

N = $1.222 \times 10^{-3}$ moles

Now, the moles of hydrogen won't change. Therefore, let us calculate volume at STP of $1.222 \times 10^{-3}$ moles of hydrogen.

Now, at STP T = 273.15 K , P = 1 atm and N = $1.222 \times 10^{-3}$ moles

$1 \times V = 1.222 \times 10^{-3} \times 0.0821 \times 273.15 K$

V = 0.027398 Litre

= $0.027398 \times 1000$ (as 1 L = 1000 ml)

= 27.398 ml

Therefore, volume of hydrogen at STP is 27.398 ml .

(c) Now, we can write the the reaction for this case as follows.

$Mg + 2HCl \rightarrow MgCl_{2} + H_{2}$

As, weight of magnesium = 0.028 grams

Molar mass of magnesium = 24.3 grams/mole

Number of moles of magnesium = $\frac{mass}{\text{molar mass}}$

= $\frac{0.028}{24.3}$

= $1.15226 \times 10^{-3}$ moles

Since, it can be seen from the reaction that

1 mole of Magnesium = 1 mole of hydrogen

and, moles of hydrogen = $1.15226 \times 10^{-3}$ moles

= 0.001523 moles

Hence, theoretical number of moles of hydrogen that can be produced from 0.028 grams of Mg is 0.001523 moles

8 0

4 years ago

Aldehydes may oxidize to form:

Arlecino [84]

Aldehydes may oxidize to form carboxylic acid exception to oxidizing formaldehyde with strong oxidizing agent.

HCHO + 3[O] = CO₂ + H₂O

5 0

3 years ago

Read 2 more answers

What is the mass of NaCl required to make 140 grams of a 12% solution of NaCl in water?

Makovka662 [10]

Answer:

C. 17 grams.

Explanation:

∵ mass % = [mass of solute/mass of solution] x 100.

mass of solute (NaCl) = ??? g & mass of solution = 140.0 g.

∴ mass of NaCl = (mass %)(mass of solution)/100 = (12.0)(140.0)/100 = 16.80 g ≅ 17.0 g.

3 0

3 years ago

Read 2 more answers

H. Identity of unknown metal

OLEGan [10]

Answer:

you can identify an unknown substance by measuring its density and comparing your results to a list of known densities. Density=mass/volume. Assume that you have to identify an unknown metal. You can determine the mass of the metal on a scale.

8 0

4 years ago

Why chemically did the prescribing of thalidomide for morning sickness in pregnant women lead to tragic consequences, including

Dominik [7]

Answer:

See explanation

Explanation:

The drug thalidomide with molecular formula C13H10N2O4 was widely prescribed by doctors for morning sickness in pregnant women in the 1960s.

The drug was sold as a racemic mixture (+)(R)-thalidomide and (-)(S)-thalidomide.

Unfortunately, only the (+)(R)-thalidomide exhibited the required effect while (-)(S)-thalidomide is a teratogen.

This goes a long way to underscore the importance of separation of enantiomers in drug production.

Therefore, all the teratogenic effects observed when using the drug thalidomide was actually as a result of the presence of (-)(S)-thalidomide, the unwanted enantiomer.

3 0

3 years ago