Answer:
Sand - A network
Dry Ice - Molecule
Lime - Ionic
Gold bar - Metallic
Explanation:
The items are;
dry ice (CO2)
lime (CaO)
gold bar (Au)
sand (SiO2)
The options are;
molecular,
an ionic,
a network,
or a metallic solid
Among the items, the only metal present is the gold bar. So it makes sense that the gold bar is matched with 'Metallic solid'.
The Calcium oxide is an 'ionic' compound as it contains the calcium ion and the oxygen ion bonded by an electrovalent bond.
Dry Ice, CO2 is a molecule composed of one carbon atom bonded to two oxygen atoms via two double bonds. So it is matched with 'Molecular'
The only option left is 'A network' and it is matched with Sand (SiO2).
The result is given as;
Sand - A network
Dry Ice - Molecule
Lime - Ionic
Gold bar - Metallic
Half-life is the time required for decay of 50% of radio-active nuclei.
Thus, when radio-active material crosses 1st half-life, 100/2 = 50% radio-active material is left and remaining 50% is elapsed.
When, when radio-active material crosses 2nd half-life, 50/2 = 25% radio-active material is left and remaining 75% is elapsed.
When radio-active material crosses 3rd half-life, 25/2 = 12.5% radio-active material is left and remaining 87.5% is elapsed.
Thus, 2 <span>half-lives must elapse until 84 % of a radioactive sample of atoms has decayed.</span>
Answer:
B
Explanation:
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The acetic acid will dissociate as
We will use Hendersen Hassalbalch's equation here
pH = pKa + log [salt] / [acid]
Where
[Acid] = concentration of protonated form
5.1 = 4.8 + log [salt] / [acid]
1.99= [salt] / [acid]
[salt] +[acid] = 0.5
1.99 [acid] + [acid] = 0.5
[acid] = 0.167 M
[acid] / total concentration = 0.167 / 0.5 = 0.33.4
So percentage = 33.4 % or approx 33 %
I’m pretty sure the answer is stir the water