Which organ system carries materials to human tissues?

Which of the following isoelectronic series is correctly ranked from largest ionic radius to smallest ionic radius? 1. N 3−, O 2

love history [14]

Answer:

Option 1: N⁻³ > O⁻² > F⁻ > Na⁺ > Mg⁺²

Explanation:

Ionic radius is the radius of an atom´s ion in ionic crystal structure. In an ion that lose an electron, to form a cation, the radius of the ion gets smaller, because the repulsion between electrons decrease because fewer electrons are present. Conversely, adding on electron to a neutral atom, to form an anion, causes electron - electron repulsions to increase, so the size of the radius of the ion gets bigger.

Isoelectronic species are ions or elements that have the same number of electrons in their electronic shells but have different overall charges, because of their different atomic numbers.

In a isolelectronic series (same number of electrons), the increase of the positive charge (given by the number of protons in the nucleus), will cause a decrease in radius beacuse the greater electrostatic attraction between the electrons and the nucleus. Consequently, the ion with the greatest nuclear charge will have the smallest ionic radius and the ion with the smallest nulear charge will have the largest ionic radius.

We will use this principle to solve our problem.

In our case, the given ions are:

N⁻³ : Z = 7, e⁻ = 10
O⁻²: Z= 8, e⁻ =10
F⁻: Z = 9, e⁻ = 10
Na⁺: Z= 11, e⁻ = 10
Mg⁺²: Z=12, e⁻ =10

where Z= number of protons, and e⁻ = number of electrons.

Hence the decreasing order of ionic radius is:

N⁻³ > O⁻² > F⁻ > Na⁺ > Mg⁺²

Have a nice day!

4 0

2 years ago

Suppose 2.8 moles of methane are allowed to react with 5 moles of oxygen.

Ronch [10]

Answer : The limiting reagent is $O_2$

Solution : Given,

Moles of methane = 2.8 moles

Moles of $O_2$ = 5 moles

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

$CH_4+2O_2\rightarrow CO_2+2H_2O$

From the balanced reaction we conclude that

As, 2 mole of $O_2$ react with 1 mole of $CH_4$

So, 5 moles of $O_2$ react with $\frac{5}{2}=2.5$ moles of $CH_4$

From this we conclude that, $CH_4$ is an excess reagent because the given moles are greater than the required moles and $O_2$ is a limiting reagent and it limits the formation of product.

Hence, the limiting reagent is $O_2$

8 0

3 years ago

What mass of lead (II) chloride is produced when 200.0 mL of a 0.250 M solution of sodium chloride is mixed with 200.0 mL of a 0

kow [346]

Answer:

Option d. 6.95 g

Explanation:

First of all, we state the reaction:

2NaCl + Pb(NO₃)₂ → PbCl₂ + 2NaNO₃

We determine the moles of each reactant, to state the limiting

Firstly we convert volume frm mL to L

0.200 L . 0.250M = 0.05 moles of NaCl

0.200L . 0.250M = 0.05 moles of Pb(NO₃)₂

Acording to stoichiometry we know that relation is 1:2, so the limiting reagent is the NaCl.

For 1 mol of Pb(NO₃)₂ I need 2 moles of NaCl

For 0.05 moles of Pb(NO₃)₂ I would need, the double → 0.1 moles

(We only have, 0.05 moles of NaCl)

Stoichiometry to the formed product is 2:1

From 2 moles of NaCl I produce 1 mol of PbCl₂

From 0.05 moles I would produce, the half → 0.025 moles

Let's convert the moles to mass → 0.025 mol . 278.1 g / 1mol = 6.95 g

8 0

3 years ago

What is the specific heat of the solid phase? (Please see picture attached)

ValentinkaMS [17]

Answer:

B.0.2 J/g°C

Explanation:

From the attached picture;

Heat attained in the solid phase is 200 Joules
Change in temperature is 50°C ( from 0°C to 50°C)
Mass of the solid is 20 g

We are required to determine the specific heat capacity of the substance;

We need to know that Quantity of heat is given by the product of mass,specific heat capacity and change in temperature.
That is; Q = mcΔT

Rearranging the formula;

c = Q ÷ mΔT

Therefore;

Specific heat = 200 J ÷ (20 g × 50°c)

= 0.2 J/g°C

Thus, the specific heat of the solid is 0.2 J/g°C

4 0

3 years ago

Which keystone species feed on other animals and prevent them from damaging the ecosystem?

Arisa [49]

Predators? I just looked it up lol

8 0

2 years ago