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omeli [17]
3 years ago
12

The radioactive isotope z has a half-life of 12 hours. after 2 days, the fraction of the original amount remaining is

Chemistry
1 answer:
nataly862011 [7]3 years ago
4 0
.5•.5•.5•.5=1/2•1/2•1/2•1/2=1/4•1/4=1/16
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Reason why chemistry is studied
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Answer: Chemistry is the study of change. Various reasons why to study Chemistry is to appreciate the fundamentals of the world such as the composition of all living thing. We are made up of matter. The interaction of sub atomic particles in an atom to form a single being. Also to understand how certain chemicals are beneficial and harmful in our lives just by reading product labels.

Explanation:

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3 years ago
To begin the experiment, 1.11g of methane CH4is burned in a bomb calorimeter containing 1000 grams of water. The initial tempera
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3 years ago
How many liters of a 0.30M solution are needed to give 2.7 moles of solute? Your answer:
OverLord2011 [107]
You HAVE TO know that molarity (M) tells you the number of moles of a solute per Liters of solution.
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8 0
3 years ago
Read 2 more answers
In each of the following sets of elements, which one will be least likely to gain or lose electrons?
klasskru [66]
1. The reactivity among the alkali metals increases as you go down the group due to the decrease in the effective nuclear charge from the increased shielding by the greater number of electrons. The greater the atomic number, the weaker the hold on the valence electron the nucleus has, and the more easily the element can lose the electron. Conversely, the lower the atomic number, the greater pull the nucleus has on the valence electron, and the less readily would the element be able to lose the electron (relatively speaking). Thus, in the first set comprising group I elements, sodium (Na) would be the least likely to lose its valence electron (and, for that matter, its core electrons).

2. The elements in this set are the group II alkaline earth metals, and they follow the same trend as the alkali metals. Of the elements here, beryllium (Be) would have the highest effective nuclear charge, and so it would be the least likely to lose its valence electrons. In fact, beryllium has a tendency not to lose (or gain) electrons, i.e., ionize, at all; it is unique among its congeners in that it tends to form covalent bonds.

3. While the alkali and alkaline earth metals would lose electrons to attain a noble gas configuration, the group VIIA halogens, as we have here, would need to gain a valence electron for an full octet. The trends in the group I and II elements are turned on their head for the halogens: The smaller the atomic number, the less shielding, and so the greater the pull by the nucleus to gain a valence electron. And as the atomic number increases (such as when you go down the group), the more shielding there is, the weaker the effective nuclear charge, and the lesser the tendency to gain a valence electron. Bromine (Br) has the largest atomic number among the halogens in this set, so an electron would feel the smallest pull from a bromine atom; bromine would thus be the least likely here to gain a valence electron.

4. The pattern for the elements in this set (the group VI chalcogens) generally follows that of the halogens. The greater the atomic number, the weaker the pull of the nucleus, and so the lesser the tendency to gain electrons. Tellurium (Te) has the highest atomic number among the elements in the set, and so it would be the least likely to gain electrons.
7 0
3 years ago
For the reaction N2O4(g) ⇋ 2NO2(g), Kc = 0.25 at 98°C. At a point during the reaction, the concentration of N2O4 = 0.50 M and th
Scilla [17]

Answer:

Q = 0.50

No

Left

Explanation:

At a generic reversible equation

aA + bB ⇄ cC + dD

The reaction coefficient (Q) is the ratio of the substances concentrations:

Q = \frac{[C]^c*[D]^d}{[A]^a*[B]^b}

Solids and liquid water are not considered in this calculus.

When the reaction achieves equilibrium (concentrations are constant), the Q value is named as Kc, which is the equilibrium constant of the reaction. If Q > Kc, it indicates that the concentration of the products is higher, so, the reaction must progress to the left and form more reactants; if Q < Kc, than the concentrations of the reactants, are higher, so, the reaction progress to the right.

In this case:

Q = \frac{[NO_2]^2}{[N_2O_4]}

Q = \frac{0.50^2}{0.50}

Q = 0.50

So, Q > Kc, the reaction is not at equilibrium and it progresses to the left.

6 0
3 years ago
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