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Kazeer [188]
3 years ago
11

PLS HELP QUICKLY I WILL GIVE 79 POINTS FOR YALL TO ANSWER THIS QUESTION!

Chemistry
1 answer:
Daniel [21]3 years ago
4 0

Answer:

Magnesium and strontium

Explanation:

11 protons and 11 electrons, 12 neutrons.

The atomic number of sodium is 11, therefore the number of electrons and protons are 11. The atomic mass is 23, and to find neutrons you need to subtract the atomic number from the atomic mass, therefore the number of neutrons are 12.

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How many moles are in 272 grams of hydrogen peroxide (H2O2) ?
Strike441 [17]

Answer:

8 moles

Explanation:

When we are asked to convert from grams of a substance into moles, we have to use the substance's molar mass.

Meaning that for this problem, we'll <em>use the molar mass of hydrogen peroxide</em> (H₂O₂), as follows:

  • 272 g ÷ 34 g/mol = 8 mol

There are 8 moles in 272 grams of hydrogen peroxide.

7 0
2 years ago
True or False ? Endothermic reactions are characterized by net absorption of thermal energy from its surroundings which leads to
Artemon [7]
False

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3 0
3 years ago
"How much NH4Cl, when present in 2.00 liters of 0.200 M ammonia, will give a solution with pH = 8.20? For NH3, Kb = 1.8 x 10-5"
Andru [333]

Answer:

245.66g of NH₄Cl is the mass we need to add to obtain the desire pH

Explanation:

The mixture of NH3/NH4Cl produce a buffer. We can find the pH of a buffer using H-H equation:

pH = pKa + log [A⁻] / [HA]

<em>Where [A⁻] is the molar concentration of the base, NH₃, and [HA] molar concentration of the acid, NH₄⁺. This molar concentration can be taken as the moles of each chemical</em>

<em />

First, we need to find pKa of NH₃ using Kb. Then, the moles of NH₃ and finally replace these values in H-H equation to solve moles of NH₄Cl we need to obtain the desire pH.

  • <em>pKa NH₃/NH₄⁺</em>

pKb = - log Kb

pKb = -log 1.8x10⁻⁵ = <em>4.74</em>

pKa = 14 - pKb

pKa = 14 - 4.74

pKa = 9.26

  • <em>Moles NH₃</em>

<em>2.00L ₓ (0.200mol NH₃ / L) = 0.400 moles NH₃</em>

  • <em>H-H equation:</em>

pH = pKa + log [NH₃] / [NH₄Cl]

8.20 = 9.26 + log [0.400 moles] / [NH₄Cl]

-1.06 =  log [0.400 moles] / [NH₄Cl]

0.0087 =  [0.400 moles] / [NH₄Cl]

[NH₄Cl] = 0.400 moles / 0.0087

[NH₄Cl] = 4.59 moles of NH₄Cl we need to add to original solution to obtain a pH of 8.20. In grams (Using molar mass NH₄Cl=53.491g/mol):

4.59 moles NH₄Cl ₓ (53.491g / mol) =

<h3>245.66g of NH₄Cl is the mass we need to add to obtain the desire pH</h3>

<em />

3 0
4 years ago
Calculate the solubility of mn(oh)2 in grams per liter when buffered at ph=7.0. assume that buffer capacity is not exhausted
Vanyuwa [196]
When PH + POH = 14 
∴ POH = 14 -7 = 7

when POH = -㏒[OH-]

          7    = -㏒ [OH-]
∴[OH-] = 10^-7

by using ICE table:

           Mn(OH)2(s) ⇄  Mn2+ (aq)  + 2OH-(aq)
initial                              0                     10^-7
change                           +X                      +2X
Equ                                 X                  (10^-7 + 2X)

when Ksp = [Mn2+][OH-]^2

when Ksp of Mn(OH)2 = 4.6 x 10^-14

by substitution:

4.6 x 10^-14 = X*(10^-7+2X)^2  by solving this equation for X

∴ X =2.3 x 10-5 M

∴ The solubility of Mn(OH)2 in grams per liter (when the molar mass of Mn(OH)2 = 88.953 g/mol
= 2.3 x10^-5 moles/L * 88.953 g/mol

= 0.002 g/ L
3 0
3 years ago
Read 2 more answers
How many moles of hydrogen are needed to completely react with 2 moles of nitrogen
Natali5045456 [20]
Assuming ammonia is the product of this reaction:

N2+3H2--->2NH3

2 mole N2 * (3 mol H2)/(1 mol N2)= 6 mol H2

You would need 6 mol of hydrogen gas to completely react with 2 mol of nitrogen. 
5 0
3 years ago
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