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3 years ago

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(worth 10pts!!!!!!) What did Dmitri Mendeleev contribute to science? A. He arranged the first periodic table. B. He developed th

e first model of the atom. C. He discovered many unknown elements . D. He developed the first atomic theory

2 answers:

MAVERICK [17]3 years ago

6 0

Answer:

A.

Explanation:

vesna_86 [32]3 years ago

3 0

Answer:

A. He arranged the first periodic table.

Explanation:

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the daily dose of ampicillin for the treatment of an ear infection is 115 mg/kg of body weight. what is the daily dose for a 43-

Lorico [155]

M=43lb = 19,5kg

If 115mg --------- is for --------- 1kg
so
x ---------- is for --------- 19,5kg

x = 19,5kg * 115mg / 1kg
x = 2242,5 mg

6 0

2 years ago

Read 2 more answers

8) Determine whether mixing each pair of the following results in a buffera. 100.0 mL of 0.10 M NH3 with 100.0 mL of 0.15 MNH4Cl

Marina86 [1]

Answer:

a. 100.0 mL of 0.10 M NH₃ with 100.0 mL of 0.15 M NH₄Cl.

c. 50.0 mL of 0.15 M HF with 20.0 mL of 0.15 M NaOH.

Explanation:

A buffer system is formed in 1 of 2 ways:

A weak acid and its conjugate base.

A weak base and its conjugate acid.

Determine whether mixing each pair of the following results in a buffer.

a. 100.0 mL of 0.10 M NH₃ with 100.0 mL of 0.15 M NH₄Cl.

YES. NH₃ is a weak base and NH₄⁺ (from NH₄Cl ) is its conjugate base.

b. 50.0 mL of 0.10 M HCl with 35.0 mL of 0.150 M NaOH.

NO. HCl is a strong acid and NaOH is a strong base.

c. 50.0 mL of 0.15 M HF with 20.0 mL of 0.15 M NaOH.

YES. HF is a weak acid and it reacts with NaOH to form NaF, which contains F⁻ (its conjugate base).

d. 175.0 mL of 0.10 M NH₃ with 150.0 mL of 0.12 M NaOH.

NO. Both are bases.

6 0

2 years ago

1. If a car is traveling 90 mi/hr, how many feet will the car travel in 1 sec? In 5 sec?

Fudgin [204]

Answer:

The car travel 660 feet

Explanation:

First convert the Speed into <u>Feet/sec</u>

Speed of the car = 90 mi/hr

1 mi = 5280 ft

In 90 miles = 90 x 5280 = 475,200 feet

1 hr = 60 min

1 min = 60 sec

So ,

1 hr = 60 x 60 sec = 3600 sec

The speed is defined as the distance traveled by the object in unit time. The formula of speed is :

$Speed =\frac{distance}{time}$

$Speed =\frac{90mi}{1hr}$ ... given

$Speed =\frac{475200 ft}{3600sec}$

Speed = 132 ft/sec

Now, time = 5 sec

$Speed =\frac{distance}{time}$

$distance =speed\times time$

$distance = 132ft/sec\times 5sec$

Distance = 660 feet

3 0

3 years ago

A cylindrical glass bottle 21.5 cm in length is filled with cooking oil of density 0.953 g/mL. If the mass of the oil needed to

jeka57 [31]

Answer:inner Diameter =9.19cm

Explanation:

Density is calculated as Mass/ Volume

therefore

Volume= Mass/ Density = 1360g/ 0.953g/ml=1,427 ml

1ml = 1cm³

1,427ml = 1,427cm³

Also We know that Volume of a cylinder = πr²h or πr²l

1,427cm³ = 3.142 x r² x 21.5 cm

r² = 1,427cm³/ (3.142 x 21.5cm)

r² =21.124cm²

$\sqrt{21.124}$ = r²

r= 4.596cm

Diameter= 2 x radius

=2 x 4.596

=9.19cm

7 0

3 years ago

According to the experimental procedure of Experiment F1, 135 microliters of acetophenone (120.15 g/mol, 1.03 g/mL) was reacted

Delicious77 [7]

Answer: The theoretical yield of 4-nitrochalcone is, $2.13\times 10^2$

Explanation : Given,

Volume of acetophenone = 135 microliters = 135 × 10⁻⁶ L = 0.135 mL

conversion used : (1 microliter = 10⁻⁶ L) and (1 L = 1000 mL)

Density of acetophenone = 1.03 g/mL

Mass of acetophenone = Density × Volume = 1.03 g/mL × 0.135 mL = 0.139 g

Mass of 4-nitrobenzaldehyde = 127 mg = 0.127 g

Conversion used : (1 mg = 0.001 g)

First we have to calculate the moles of acetophenone and 4-nitrobenzaldehyde

$\text{Moles of acetophenone}=\frac{\text{Given mass acetophenone}}{\text{Molar mass acetophenone}}$

$\text{Moles of acetophenone}=\frac{0.139g}{120.15g/mol}=0.00116mol$

and,

$\text{Moles of 4-nitrobenzaldehyde}=\frac{\text{Given mass 4-nitrobenzaldehyde}}{\text{Molar mass 4-nitrobenzaldehyde}}$

$\text{Moles of 4-nitrobenzaldehyde}=\frac{0.127g}{151.12g/mol}=0.000840mol$

Now we have to calculate the limiting and excess reagent.

The balanced chemical equation is:

$C_8H_8O+C_7H_5NO_3\rightarrow C_{15}H_{11}NO_3$

From the balanced reaction we conclude that

As, 1 mole of 4-nitrobenzaldehyde react with 1 mole of acetophenone

So, 0.000840 mole of 4-nitrobenzaldehyde react with 0.000840 mole of acetophenone

From this we conclude that, acetophenone is an excess reagent because the given moles are greater than the required moles and 4-nitrobenzaldehyde is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of 4-nitrochalcone

From the reaction, we conclude that

As, 1 mole of 4-nitrobenzaldehyde react to give 1 mole of 4-nitrochalcone

So, 0.000840 mole of 4-nitrobenzaldehyde react to give 0.000840 mole of 4-nitrochalcone

Now we have to calculate the mass of 4-nitrochalcone

$\text{ Mass of 4-nitrochalcone}=\text{ Moles of 4-nitrochalcone}\times \text{ Molar mass of 4-nitrochalcone}$

Molar mass of 4-nitrochalcone = 253.25 g/mole

$\text{ Mass of 4-nitrochalcone}=(0.000840moles)\times (253.25g/mole)=0.21273g=212.73mg=2.13\times 10^2mg$

(1 g = 1000 g)

Therefore, the theoretical yield of 4-nitrochalcone is, $2.13\times 10^2mg$

4 0

3 years ago