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3 years ago

5

When Kristen was five, she became sick with chickenpox and then recovered. What claim explains why Kristen is unlikely to get ch

ickenpox a second time? *
A. Kristen has developed a vaccine against chickenpox.
B. Kristen has not developed antibodies to chickenpox.
C. Kristen’s body no longer contains cells that can be damaged by chickenpox.
D. Kristen’s body has memory cells that will produce antibodies to fight chickenpox.
be quick plz!!

2 answers:

VLD [36.1K]3 years ago

5 0

Answer:

the answer is A!

Mark as brainless

Rudik [331]3 years ago

5 0

Answer:

A. Kristen has developed a vaccine against chickenpox

Please mark me as brainliest( ^ω^ )

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What mass of potassium hypochlorite (FW-90.6 g/mol) must be added to 4.50 x 10 mL of water to give a solution with pH 10.20? [Ka

marta [7]

Answer : The mass of potassium hypochlorite is, 4.1 grams.

Explanation : Given,

pH = 10.20

Volume of water = $4.50\times 10^2ml=0.45L$

The decomposition of KClO will be :

$KClO\rightarrow K^++ClO^-$

Now the further reaction with water $(H_2O)$ to give,

$ClO^-+H_2O\rightarrow HClO+OH^-$

First we have to calculate the pOH.

$pH+pOH=14\\\\pOH=14-pH\\\\pOH=14-10.20=3.8$

Now we have to calculate the $OH^-$ concentration.

$pOH=-\log [OH^-]$

$3.8=-\log [OH^-]$

$[OH^-]=1.58\times 10^{-4}M$

Now we have to calculate the base dissociation constant.

Formula used : $K_b=\frac{K_w}{K_a}$

Now put all the given values in this formula, we get :

$K_b=\frac{1.0\times 10^{-14}}{4.0\times 10^{-8}}=2.5\times 10^{-7}$

Now we have to calculate the concentration of $ClO^-$ .

The equilibrium constant expression of the reaction is:

$K_b=\frac{[OH^-][HClO]}{[ClO^-]}$

As we know that, $[OH^-]=[HClO]=1.58\times 10^{-4}M$

$2.5\times 10^{-7}=\frac{(1.58\times 10^{-4})^2}{[ClO^-]}$

$[ClO^-]=0.0999M$

Now we have to calculate the moles of $ClO^-$ .

$\text{Moles of }ClO^-=\text{Molarity of }ClO^-\times \text{Volume of solution}$

$\text{Moles of }ClO^-=0.0999mole/L\times 0.45L=0.0449mole$

As we know that, the number of moles of $ClO^-$ are equal to the number of moles of KClO.

So, the number of moles of KClO = 0.0449 mole

Now we have to calculate the mass of KClO.

$\text{Mass of }KClO=\text{Moles of }KClO\times \text{Molar mass of }KClO$

$\text{Mass of }KClO=0.0449mole\times 90.6g/mole=4.07g\approx 4.1g$

Therefore, the mass of potassium hypochlorite is, 4.1 grams.

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Who has the greater boiling point C2H6or C2H50H

hichkok12 [17]

Answer:

C2H5OH has a greater boiling point.

Explanation:

It is a bigger molecule than C2H6.

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A titration of 0.1 M NaOH into 1.2 L of HCl was stopped once the pH reached 7 (at 25C). If 0.4 L of NaOH needed to be added to a

MArishka [77]

Answer:

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0.04 moles of HCl are in 1.2 L. The molarity of HCl is:

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Magnetism, or more specifically electromagnetic repulsion

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KMnO4<br><br> Assign oxidation numbers to each element in this compound.

zysi [14]

K=+1

Mn= +7

O= -2

That’s it!!!

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