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3 years ago

The isotope Np-238 has a half life of 2.0 days if 96 grams of it were present on Monday how much will remain six days later

Chemistry

1 answer:

Neporo4naja [7]3 years ago

4 0

Answer:

12 grams

Explanation:

For any radioactive substance

the amount of substance left after n half life is given by = $x/2^n$

where x the original amount of substance.

____________________________________________

Half life of isotope Np-238 = 2 days

total no of days = 6

no of half life =total no of days/Half life of isotope Np-238 = 6/2 = 3

thus,

for our problem n = 3

initial amount of Np-238 = 96 grams

thus,

the amount of substance left after 3 half life = 96/2^3 = 96/8 = 12 grams.

Thus, 12 grams will be left after six days.

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3 years ago

If an element has 2+ valence electrons, does it transfer only one or more than one valence electrons

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Answer:

element having 2+ valence electrons can transfer its more than one electron that is 2 electron completely.

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Group IIA have 2+ valency and two electrons in its valance shell.

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Element of IIA form ionic with most electronegative element.

Examples:

Cu²⁺, Mg²⁺, Sr²⁺ are examples having 2+ valance electron

one of the following is examples of element that have 2+ valence electrons

MgCl₂

Atomic number of Magnesium (Mg) is 12

Electronic Configuration of Mg:

1s², 2s², 2p⁶, 3s²

K =2

L = 8

M = 2

So, it have to give its 2 electrons to form a stable compound.

Similarly

Chlorine atomic number is 17

Electronic Configuration of Chlorine:

1s², 2s², 2p⁶, 3s², 3p⁵

K =2

L = 8

M = 7

So, it have to gain one electrons to form a stable compound and complete its octet.

So,

Two chlorine atom as a molecule gain 2 electrons from Mg²⁺ atom

So one Mg²⁺ and 2 Cl⁻ atoms form an ionic bond

where in this ionic bond Mg²⁺ transfer its 2 valence electron completely and chlorine molecule accept 2 electrons.

Cl-----Mg------Cl

So the Answer is

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2 years ago

Hydrocyanic acid, HCN, is a weak acid. (a) Write the chemical equation for the dissociation of HCN in water. (b) Identify the Br

12345 [234]

Answer: a) $HCN(aq.)+H_2O\rightleftharoons H_3O^+(aq.)+CN^-(aq.)$

b) $HCN$ : acid $CN^-$ :conjugate base.

And, $H_2O$ : base $H_3O^+$ : conjugate acid.

c) $HCN(aq.)+NaOH(aq)\rightleftharoons NaCN(aq.)+H_2O(l)$

d) $NaCN(aq)\rightarrow Na^+(aq.)+CN^-(aq)$

e) $NaCN(aq)+HCl(aq)\rightarrow NaCl(aq.)+HCN(aq)$

Explanation:

a) Weak acid is defined as the acid which does not completely dissociates when dissolved in water. They have high pH. These releases $H^+$ ions in their aqueous states.

The equation for the dissociation of $HCN$ acid is given by:

$HCN(aq.)+H_2O\rightleftharoons H_3O^+(aq.)+CN^-(aq.)$

b) According to the Bronsted-Lowry conjugate acid-base theory, an acid is defined as a substance which looses donates protons and thus forming conjugate base and a base is defined as a substance which accepts protons and thus forming conjugate acid.

For the given chemical equation:

$HCN$ is loosing a proton, thus it is considered as an acid and after losing a proton, it forms $CN^-$ which is a conjugate base.

And, $H_2O$ is gaining a proton, thus it is considered as a base and after gaining a proton, it forms $H_3O^+$ which is a conjugate acid.

c) Neutralization reaction is a reaction in which an acid reacts with base to produce salt and water.

$HCN(aq.)+NaOH(aq)\rightarrow NaCN(aq.)+H_2O(l)$

d) The chemical equation for dissociation of $NaCN$ in water.

$NaCN(aq)\rightarrow Na^+(aq.)+CN^-(aq)$

e) The chemical equation for the reaction of $NaCN$ and $HCI$

$NaCN(aq)+HCl(aq)\rightarrow NaCl(aq.)+HCN(aq)$

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3 years ago