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notka56 [123]
3 years ago
7

which of the following substances is least able to cross the blood-brain barrier.)a. waterb. sodium ionsc glucosed. white blood

cells
Chemistry
1 answer:
ivolga24 [154]3 years ago
8 0

Answer:

d. white blood cells

Explanation:

It is the white blood cells that have the least tendency to cross the blood- brain barrier.

Blood- brain barrier is psychological barrier and restricts substances that circulate into the blood from crossing over the central nervous system.

Water, glucose as well as sodium ions can easily cross the barrier. As these are good for body supply energy to the brain.

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Hydrogen gas, iodine vapor, hydrogen iodine are mixed in a flask and heated to 696°C. H2(g) + I2(g) ⇋ 2 HI(g) Kc = 52 at 696°C I
Anettt [7]

Answer: The equilibrium concentration of hydrogen gas is 0.0269 M

Explanation:

The chemical reaction follows the equation:

                  H_2(g)+I_2(g)\rightleftharpoons 2HI(g)

At t = 0          0.044M     0.044M              0.177M  

At t=t_{eq}    (0.044-x)M    (0.044-x)M      (0.177+x)M

The expression for K_c for the given reaction follows:

K_c=\frac{[HI]^2}{[H_2]\times [I_2]}

We are given:

K_c=52

Putting values in above equation, we get:

52=\frac{(0.177+x)^2}{(0.044-x)^2}

x=0.0171M

Hence, the equilibrium concentration of hydrogen gas is (0.044-x) M =(0.044-0.0171) M= 0.0269 M

7 0
2 years ago
Which of the following elements belong to the same pair?
butalik [34]

Answer:

B. Na and Li

Both are group I elements.

5 0
2 years ago
put the contributions to the understanding of the atomic structure in order from most recent at the top to the earliest at the b
r-ruslan [8.4K]

Answer:

From Top to Bottom:

- Democritus coming up with the concept of an atom

- Dalton discovering that atoms are the smallest part of an element

- Rutherford discovering the nucleus of an atom

- Thomson discovering electrons

- Bohr modeling electrons orbiting the nucleus

- Schrodinger modeling electrons in the electron cloud

Explanation:

The best way to think about this is from the inside out. Democrats (who lived long before any of the other scientists mentioned) was the one who thought of the idea of the atom. - Therefore, this must be first because all other choices are elaborations on the idea that atoms exist. Next must be Dalton. Dalton saw atoms as "cannonballs" if you will; a solid mass. So then after that, Rutherford and his gold foil experiment (he discovered that some rays he shot through gold foil were deflected back; ie the existence of concentrated areas in an atom, ie the nucleus). Then we get into the information on electrons. We must start with discovery (Thomson). Heres where it gets complicated. Electrons don't <em>actually </em>orbit the nucleus, they exist in electron clouds. So it would be Bohr, who came up with the idea that electron exist outside the nucleus, then Schrodinger, who elaborated on Bohr's theory. Hope this helps!

Nat, Junior

Accel + AP Chem student

5 0
1 year ago
What is the balanced equation for H3PO4=H4P2O7+H2O
podryga [215]

Answer:

2H3PO4=H4P2O7+H2O

Explanation:

2H3PO4=H4P2O7+H2O

5 0
3 years ago
Complete the acid–base equation for the dissolution of the following compound into liquid HF solvent. The relevant pKa values ar
LenKa [72]

Answer:

The balanced chemical equation: NH₃ + 2 HF → NH₄⁺ + HF₂⁻

Explanation:

According to the Brønsted–Lowry acid–base theory, the acid- base reaction is a type of chemical reaction between the acid and base to give a conjugate acid and a conjugate base.

In this reaction, a Brønsted–Lowry acid loses a proton to form a conjugate base. Whereas, a Brønsted–Lowry base accepts a proton to form a conjugate acid.

Acid + Base ⇌ Conjugate Base + Conjugate Acid

The acid dissociation constant (Kₐ) <em>signifies the acidic strength of a chemical species.</em>

∵ pKₐ = - log Kₐ

Thus for a strong acid, Kₐ value is large and pKₐ value is small.

pKₐ (HF) = 3.2 → strong acid

pKₐ (NH₃) = 38 → weak acid

<u>The chemical reaction involved in the dissolution process:</u>

NH₃ + 2 HF → NH₄⁺ + HF₂⁻

In this acid-base reaction, the acid HF reacts with NH₃ base to give the conjugate base HF₂⁻ and conjugate acid NH₄⁺.

<u>HF (acid) donates a proton to form the conjugate base, HF₂⁻ ion. NH₃ (base) accepts a proton to form the conjugate acid. </u>

7 0
3 years ago
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