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3 years ago

Wch of the following phrases is the best definition of science?

Chemistry

2 answers:

krek1111 [17]3 years ago

7 0

Answer: A i think

Explanation:

andrew-mc [135]3 years ago

5 0

A because

that would make the very most sense and i saw that someone else had that answer and i need the points sorry not sorry i can’t believe they have a 20 charater limit like what the heck man 1 word and im gone all i wanted to say was A buttttt NOOOOO

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A container with 3.0 moles of gas has a volume of 60.0L with a temperature at 400.K what is the pressure

iris [78.8K]

Answer: P= 1.64 atm

Explanation: solution attached.

Use Ideal gas law

PV= nRT

Derive for P

P= nRT/V R= 0.08205 L.atm/mol.K

Substitute the values.

3 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

Chemistry question! Please help!

Illusion [34]

When a solid (solute) comes in contact with the liquid (solvent), the solute goes about C) dissolution, in which the solid dissolves into the liquid.

7 0

3 years ago

Read 2 more answers

A sample of oxide iron weighing 2.40g was heated in a stream of hydrogen until it was completely converted to the metal. If the

wlad13 [49]

Answer:

Fe₂O₃

Explanation:

To solve this question we must find the moles of Iron in 1.68g. With the difference of the masses we can find the moles of oxygen. The formula will be obtained with the ratio of both amount of moles:

Moles Fe:

1.68g * (1mol / 56g) =0.03moles

Moles O:

2.40g-1.68g = 0.72g * (1mol/16g) = 0.045moles

The ratio O/Fe is:

0.045moles / 0.03moles = 1.5 moles. this ratio is obtained if the formula is:

4 0

3 years ago

What masses of monobasic and dibasic sodium phosphate will you use to make 250 mL of 0.1 M sodium phosphate buffer, pH = 7?

Oduvanchick [21]

Answer:

Mass of monobasic sodium phosphate = 1.857 g
Mass of dibasic sodium phosphate = 1.352 g

Explanation:

The equilibrium that takes place is:

H₂PO₄⁻ ↔ HPO₄⁻² + H⁺ pka= 7.21 (we know this from literature)

To solve this problem we use the Henderson–Hasselbalch (H-H) equation:

pH = pka + $log\frac{[A^{-} ]}{[HA]}$

In this case [A⁻] is [HPO₄⁻²], [HA] is [H₂PO₄⁻], pH=7.0, and pka = 7.21

If we use put data in the H-H equation, and solve for [HPO₄⁻²], we're left with:

$7.0=7.21+log\frac{[HPO4^{-2} ]}{[H2PO4^{-} ]}\\ -0.21=log\frac{[HPO4^{-2} ]}{[H2PO4^{-} ]}\\\\10^{-0.21} =\frac{[HPO4^{-2} ]}{[H2PO4^{-} ]}\\0.616 * [H2PO4^{-}] = [HPO4^{-2}]$

From the problem, we know that [HPO₄⁻²] + [H₂PO₄⁻] = 0.1 M

We replace the value of [HPO₄⁻²] in this equation:

0.616 * [H₂PO₄⁻] + [H₂PO₄⁻] = 0.1 M

1.616 * [H₂PO₄⁻] = 0.1 M

[H₂PO₄⁻] = 0.0619 M

With the value of [H₂PO₄⁻] we can calculate [HPO₄⁻²]:

[HPO₄⁻²] + 0.0619 M = 0.1 M

[HPO₄⁻²] = 0.0381 M

With the concentrations, the volume and the molecular weights, we can calculate the masses:

Molecular weight of monobasic sodium phosphate (NaH₂PO₄)= 120 g/mol.
Molecular weight of dibasic sodium phosphate (Na₂HPO₄)= 142 g/mol.

mass of NaH₂PO₄ = 0.0619 M * 0.250 L * 120 g/mol = 1.857 g

mass of Na₂HPO₄ = 0.0381 M * 0.250 L * 142 g/mol = 1.352 g

5 0

3 years ago