Chemistry, 26.03.2020 05:57 jaydenjohnson6310

When 93 mL of distilled water is added to 188 mL of 2.91 M MgCl2, what is the new concentration?
Answer to 2 decimal places.

Answers: 3

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Answers

Answer from: sophiav9627

Explanation:

The concentration is 2.91 moles / Liter.

The moles don't change when the new water of 93mL is added.

Starting number of moles

C = 2.91 moles / Liter

m = ?

V = 1 Liter. = 1000 mL

C = m/V

2.91 moles / L = m/1 Liter

2.91 moles in 1 Liter

Moles in 188 mL

2.91 moles / 1000 mL = x moles / 188 mL Cross multiply

2.91 moles * 188 mL = 1000 x

547 moles mL = 1000 mL x Divide by 1000

547 moles mL

= x

1000 mL

0.547 moles in 188 mL

Now add 93 mL to 188 mL

281 mL

Finally calculate the concentration.

C = 0.547 moles / 281 mL

C = 0.00194 moles / mL

C = 1.93 moles / L

Answer from: Quest

assuming that your periodic table has eighteen columns, you should highlight the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.