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3 years ago

Adenine (a) pairs with a: cytosine (c) B: Guanine (g) C: Thymine (T)

2 answers:

7 0

Adenine pairs with Thymine because they have a common hydrogen bond.
Guanine and Cytosine are the other pair, don't forget.

Artist 52 [7]3 years ago

3 0

Adenine pairs with Thymine and Guanine pairs with Cytosine. I remember this by the car (C) goes in the garage (G). Then A and T are the only ones left, so they pair together.

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A pandas course fur is made out of cells as is its skin,nerves,brain this is an example of what characteristic of life

Alenkasestr [34]

i believe the answer is D, please lmk if it is incorrect!

7 0

3 years ago

The isotope 90_Sr has a half-life of 28.8 years. What is the activity, measured in atoms/second of a 50 mg sample of "Sr? (10 pt

blsea [12.9K]

Answer:

$2.5523\times 10^{11} atoms/seconds$ is the activity, measured in of a 50 mg sample of 90-Sr.

Explanation:

Half life of the 90-Sr , $t_{1/2}= 28.8 years$

Activity coefficient of the 90-Sr = $\lambda$

$\lambda =\frac{0.693}{28.8 years}=0.0240625 year^{-1}$

Mass of 90-Sr = 50 mg = 0.050 g

Molecular mass of 90-Sr = 90 g/mol

Moles of 90-Sr = $\frac{0.050 g}{90 g/mol}=0.0005555 mol$

Number of atom in 0.0005555 moles of 90-Sr:

$0.0005555 mol\times 6.022\times 10^{23} mol^{-1}=3.3455\times 10^{20} atoms$

$\lambda =0.0240625 year^{-1}=\frac{0.0240625}{3.154\times 10^7 s}=7.6292\times 10^{-10} s^{-1}$

1 year = $3.154\times 10^7 seconds$

Activity measured in atoms per seconds:

= Number of atoms × $\lambda$

$=3.3455\times 10^{20} atoms\times 7.6292\times 10^{-10} s^{-1}$

$=2.5523\times 10^{11} atoms/s$

5 0

3 years ago

2. This is like a mountain but smaller. A. valley B. hill C. plateau D. plain

dimaraw [331]

Answer:

hill

Explanation:

7 0

3 years ago

Read 2 more answers

Two or more substances that are blended together but not chemically combined make up a(n) _____.

Dahasolnce [82]

Make up a mixture.

Example is water and sand, it is blended together but not chemically. It is by physical combination of just addition of the two substances.

But if it elements are chemically combined a compound would be formed.

5 0

3 years ago

H2(g) + F2(g)2HF(g) Using standard thermodynamic data at 298K, calculate the entropy change for the surroundings when 2.20 moles

abruzzese [7]

Answer: The value of $\Delta S^o$ for the surrounding when given amount of hydrogen gas is reacted is -31.02 J/K

Explanation:

Entropy change is defined as the difference in entropy of all the product and the reactants each multiplied with their respective number of moles.

The equation used to calculate entropy change is of a reaction is:

$\Delta S^o_{rxn}=\sum [n\times \Delta S^o_{(product)}]-\sum [n\times \Delta S^o_{(reactant)}]$

For the given chemical reaction:

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

The equation for the entropy change of the above reaction is:

$\Delta S^o_{rxn}=[(2\times \Delta S^o_{(HF(g))})]-[(1\times \Delta S^o_{(H_2(g))})+(1\times \Delta S^o_{(F_2(g))})]$

We are given:

$\Delta S^o_{(HF(g))}=173.78J/K.mol\\\Delta S^o_{(H_2)}=130.68J/K.mol\\\Delta S^o_{(F_2)}=202.78J/K.mol$

Putting values in above equation, we get:

$\Delta S^o_{rxn}=[(2\times (173.78))]-[(1\times (130.68))+(1\times (202.78))]\\\\\Delta S^o_{rxn}=14.1J/K$

Entropy change of the surrounding = - (Entropy change of the system) = -(14.1) J/K = -14.1 J/K

We are given:

Moles of hydrogen gas reacted = 2.20 moles

By Stoichiometry of the reaction:

When 1 mole of hydrogen gas is reacted, the entropy change of the surrounding will be -14.1 J/K

So, when 2.20 moles of hydrogen gas is reacted, the entropy change of the surrounding will be = $\frac{-14.1}{1}\times 2.20=-31.02J/K$

Hence, the value of $\Delta S^o$ for the surrounding when given amount of hydrogen gas is reacted is -31.02 J/K

7 0

3 years ago