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8090 [49]
3 years ago
8

If a sample of DNA contained 20% cytosine, what percentage of guaninewould be in this sample and what percentage of adenine woul

d be in the sample
Chemistry
1 answer:
timofeeve [1]3 years ago
7 0
Guanine and Cytosine are complementary pairs in the DNA molecule (which means that Cytosine is bonded via hydrogen bonds to Guanine).  This is the same for Adenine and Thymine.  As such if a sample of DNA contains 20% Cytosine then it also contains approximately 20% Guanine.

The percentage of Thymine + Adenine would be 100% - 40% = 60%... Since this 60% should be equally shared between Thymine and Adenine then it implies that the percentage Adenine would be approximately 30%.
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One method used commercially to peel potatoes is to soak them in a solution of NaOH for a short time and then remove them from t
sergij07 [2.7K]

Answer:

b. 2.28 M

Explanation:

The reaction of neutralization of NaOH with H2SO4 is:

2NaOH + H2SO4 → Na2SO4 + 2H2O

<em>Where 2 moles of NaOH react per mole of H2SO4</em>

<em />

To solve the concentration of NaOH we need to find the moles of H2SO4. Using the chemical equation we can find the moles of NaOH that react and with the volume the molar concentration as follows:

<em>Moles H2SO4:</em>

45.7mL = 0.0457L * (0.500mol/L) = 0.02285 moles H2SO4

<em>Moles NaOH:</em>

0.02285 moles H2SO4 * (2moles NaOH / 1 mol H2SO4) = 0.0457moles NaOH

<em>Molarity NaOH:</em>

0.0457moles NaOH / 0.020L =

2.28M

Right option:

<h3>b. 2.28 M</h3>
7 0
3 years ago
An unknown acid solution has PH 3.4. 66% of the acid is ionized. Whats the pka?
juin [17]

Answer:

pKa=3.58

Explanation:

Hello,

In this case, since the pH defines the concentration of hydrogen:

pH=-log([H^+])

[H^+]=10^{-pH}=10^{-3.4}=3.98x10^{-4}

And the percent ionization is:

\% \ ionization=\frac{[H^+]}{[HA]}*100\%

We compute the concentration of the acid, HA:

[HA]=\frac{[H^+]}{\% \ ionization}*100\%=\frac{3.98x10^{-4}}{66\%}  *100\%\\\\

[HA]=6.03x10^{-4}

Thus, the Ka is:

Ka=\frac{[H^+][A^-]}{[HA]}=\frac{3.98x10^{-4}*3.98x10^{-4}}{6.03x10^{-4}}\\  \\Ka=2.63x10^{-4}

So the pKa is:

pKa=-log(Ka)=-log(2.63x10^{-4})\\\\pKa=3.58

Regards.

5 0
3 years ago
The reaction of hydrogen(g) with fluorine(g) to form hydrogen fluoride(g) proceeds as follows: H2(g) + F2(g) 2 HF(g) When 0.647
Nata [24]

<u>Answer:</u> The value of \Delta H for the reaction will be -537 kJ

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}

Given mass of hydrogen gas = 0.647 g

Molar mass of hydrogen gas = 2 g/mol

Putting values in above equation, we get:

\text{Moles of hydrogen gas}=\frac{0.647g}{2g/mol}=0.324mol

We are given:

Energy released for 0.324 moles of hydrogen reacted is 174 kJ

For the given chemical reaction:

H_2(g)+F_2(g)\rightarrow 2HF(g)

By Stoichiometry of the reaction:

When 0.324 moles of hydrogen gas is reacted, the energy evolved is 174 kJ

So, when 1 mole of hydrogen gas will react, the energy evolved will be = \frac{174kJ}{0.324mol}\times 1mol=537kJ

<u>Sign convention of heat:</u>

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

Hence, the value of \Delta H for the reaction will be -537 kJ

6 0
3 years ago
How are fossils formed
creativ13 [48]
I am sure the answer is D
7 0
3 years ago
What is the charge on an atom with an equal number of protons and electrons?
dexar [7]

Answer: the answer is a netrual bond

Explanation: a netural bond happens when the number of electrons are the same as the number of protons.

7 0
3 years ago
Read 2 more answers
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