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2 years ago

Science please help me!!!!

Chemistry

1 answer:

balu736 [363]2 years ago

7 0

1)Atoms are the basic units of matter and the defining structure of elements. Atoms are made up of threeparticles: protons, neutrons and electrons. Protons and neutrons are heavier than electrons and reside in the center of the atom, which is called the nucleus.

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Explain whether nuclear or mitochondrial DNA is better for identifying a specific person

hodyreva [135]

Answer:-

Nuclear DNA is inherited from all ancestors. But mitochondrial DNA is inherited from a single lineage. The DNA inside of mitochondria (called mtDNA) unlike DNA inside the nucleus, comes from only mothers.

It is not a mixture of our parent’s DNA, and each person’s mtDNA is nearly identical to his or her mother’s mtDNA.

Thus only nDNA being more unique is more useful for identifying in forensics. In cases where nDNA is not sufficient, mtDNA is used.

7 0

3 years ago

Explain why organisms are more likely to be well preserved in mud than in sand

Vsevolod [243]

Mud has alot of water so it's easier for them to live in.

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3 years ago

Your job is to determine the concentration of ammonia in a commercial window cleaner. In the titration of a 25.0 mL sample of th

ruslelena [56]

Answer:

The initial concentration of ammonia is 0.14 M and the pH of the solution at equivalence point is 5.20

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}$ .....(1)

Molarity of HCl solution = 0.164 M

Volume of solution = 23.8 mL = 0.0238 L (Conversion factor: 1 L = 1000 mL)

Putting values in equation 1, we get:

$0.164M=\frac{\text{Moles of HCl}}{0.0238L}\\\\\text{Moles of HCl}=(0.146mol/L\times 0.0238L)=0.0035mol$

The chemical equation for the reaction of ammonia and HCl follows:

$NH_3+HCl\rightarrow NH_4^++Cl^-$

By Stoichiometry of the reaction:

1 mole of HCl reacts with 1 mole of ammonia

So, 0.0035 moles of HCl will react with = $\frac{1}{1}\times 0.0035=0.0035mol$ of ammonia

Calculating the initial concentration of ammonia by using equation 1:

Moles of ammonia = 0.0035 moles

Volume of solution = 25 mL = 0.025 L

Putting values in equation 1, we get:

$\text{Initial concentration of ammonia}=\frac{0.0035mol}{0.025L}=0.14M$

By Stoichiometry of the reaction:

1 mole of ammonia produces 1 mole of ammonium ion

So, 0.0035 moles of ammonia will react with = $\frac{1}{1}\times 0.0035=0.0035mol$ of ammonium ion

Calculating the concentration of ammonium ion by using equation 1:

Moles of ammonium ion = 0.0035 moles

Volume of solution = [23.8 + 25] mL = 48.8 mL = 0.0488 L

Putting values in equation 1, we get:

$\text{Molarity of ammonium ion}=\frac{0.0035mol}{0.0488L}=0.072M$

To calculate the acid dissociation constant for the given base dissociation constant, we use the equation:

$K_w=K_b\times K_a$

where,

$K_w$ = Ionic product of water = $10^{-14}$

$K_a$ = Acid dissociation constant

$K_b$ = Base dissociation constant = $1.8\times 10^{-5}$

$10^{-14}=1.8\times 10^{-5}\times K_a\\\\K_a=\frac{10^{-14}}{1.8\times 10^{-5}}=5.55\times 10^{-10}$

The chemical equation for the dissociation of ammonium ion follows:

$NH_4^+\rightarrow NH_3+H^+$

The expression of $K_a$ for above equation follows:

$K_a=\frac{[NH_3][H^+]}{[NH_4^+]}$

We know that:

$[NH_3]=[H^+]=x$

$[NH_4^+]=0.072M$

Putting values in above expression, we get:

$5.55\times 10^{-10}=\frac{x\times x}{0.072}\\\\x=6.32\times 10^{-6}M$

To calculate the pH concentration, we use the equation:

$pH=-\log[H^+]$

We are given:

$[H^+]=6.32\times 10^{--6}M$

$pH=-\log (6.32\times 10^{-6})\\\\pH=5.20$

Hence, the initial concentration of ammonia is 0.14 M and the pH of the solution at equivalence point is 5.20

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3 years ago

Who is the Administrator of Brainly?? Hopefully, someone will answer (◍•ᴗ•◍)❤

sleet_krkn [62]

Answer:

Hey mate....

Explanation:

This is ur answer....

Kavisharma/ Haezel is the admin of brainly......

hope it helps,

mark me as the brainliest.....

Follow me......xd

3 0

3 years ago

Read 2 more answers

Many of the stars we see in the night sky are called blue giants. They put out more energy and burn millions of times brighter t

Bumek [7]

Answer:

Because it is closer to earth than the other blue giant stars.

Explanation:

The sun is closer to earth than any other big star which means we see it bigger.

6 0

3 years ago