1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
dangina [55]
3 years ago
8

Which of these pairs of elements have the same number of valence electrons

Chemistry
1 answer:
erastovalidia [21]3 years ago
6 0
Beryllium (Be) and Calcium (Ca)
You might be interested in
1.this substance is a natural non-living material with a uniform structure throughout
vovikov84 [41]
1.Mineral
2.Igneous
3.Composition

7 0
3 years ago
Read 2 more answers
The absorbance of an equilibrium mixture containing FeSCN2 was measured at 447 nm and found to be 0.347. What is the equilibrium
Ksenya-84 [330]

Answer:

The concentration is C = 1.11 mol/L

Explanation:

From the question we are told that

     The absorbance is  A = 0.347

       The length is  l =  447 nm  =  447 *10^{-7} \ cm

     

Generally absorbance is mathematically represented as

        A =  \epsilon*  C * l

where \epsilon is the molar absorptivity of  FeSCN2  with a value \epsilon  =  7.0*10^3 L/cm/mol

 and  C is the equilibrium concentration of FeSCN2

So  

       C = \frac{A}{\epsilon *  l  }

substituting values

        C = \frac{0.347}{7.0*10^{3} *  447 *10^{-7}  }

         C = 1.11 mol/L

5 0
3 years ago
Which of the following is not true?
WITCHER [35]
There r three fundamental forces in nature
4 0
3 years ago
5)
Kryger [21]

The empirical formula : C₁₂H₄F₇

The molecular formula : C₂₄H₈F₁₄

<h3>Further explanation</h3>

mol C (MW=12 g/mol)

\tt \dfrac{18.24}{12}=1.52

mol H(MW=1 g/mol) :

\tt \dfrac{0.51}{1}=0.51

mol F(MW=19 g/mol)

\tt \dfrac{16.91}{19}=0.89

mol ratio of C : H : O =1.52 : 0.51 : 0.89=3 : 1 : 1.75=12 : 4 : 7

Empirical formula : C₁₂H₄F₇

(Empirical formula)n=molecular formula

( C₁₂H₄F₇)n=562 g/mol

(12.12+4.1+7.19)n=562

(281)n=562⇒ n =2

Molecular formula : C₂₄H₈F₁₄

6 0
3 years ago
A chemistry graduate student is given of a chlorous acid solution. Chlorous acid is a weak acid with . What mass of should the s
DerKrebs [107]

Answer:

11.31g NaClO₂

Explanation:

<em> Is given 250mL of a 1.60M chlorous acid HClO2 solution. Ka is 1.110x10⁻². What mass of NaClO₂ should the student dissolve in the HClO2 solution to turn it into a buffer with pH =1.45? </em>

It is possible to answer this question using Henderson-Hasselbalch equation:

pH = pKa + log₁₀ [A⁻] / [HA]

<em>Where pKa is -log Ka = 1.9547; [A⁻] is the concentration of the conjugate base (NaClO₂), [HA] the concentration of the weak acid</em>

You can change the concentration of the substance if you write the moles of the substances:

[Moles HClO₂] = 250mL = 0.25L×(1.60mol /L) = <em>0.40 moles HClO₂</em>

Replacing in H-H expression, as the pH you want is 1.45:

1.45 = 1.9547 + log₁₀ [Moles NaClO₂] / [0.40 moles HClO₂]

-0.5047 = log₁₀ [Moles NaClO₂] / [0.40 moles HClO₂]

<em>0.3128 = </em>[Moles NaClO₂] / [0.40 moles HClO₂]

0.1251 = Moles NaClO₂

As molar mass of NaClO₂ is 90.44g/mol, mass of 0.1251 moles of NaClO₂ is:

0.1251 moles NaClO₂ ₓ (90.44g / mol) =

<h3>11.31g NaClO₂</h3>
5 0
3 years ago
Other questions:
  • If an ice cube melts at 0oC but water also freezes at 0oC, what is the difference between melting and freezing in terms of (a) t
    8·1 answer
  • Review the equation below. 2KClO3 mc012-1.jpg 2KCl + 3O2 How many moles of oxygen are produced when 2 mol of potassium chlorate
    15·2 answers
  • How many liters of 1.5 M HCl solution would react completely with 2.5 moles Ca(OH)2? (2 points)
    12·1 answer
  • Define shielding and effective nuclear charge. What is the connection between the two?
    6·1 answer
  • what actually is left over of water once it self ionizes? Like what exactly are the hydrogen and hydroxide ions? Do they remain
    8·1 answer
  • An object has a density of 2.0g/cm3. If the object were cut in half what would be the density of one of the pieces?
    12·1 answer
  • What is the cloud of gases that forms around the nucleus of a comet called?
    5·1 answer
  • What is the difference between the solid line and the dotted line?
    6·1 answer
  • What is the amount of space that a gas takes up called?
    13·1 answer
  • A clear, pure liquid sample is brought into the lab and exposed to an electrical current. Different gases are produced on each o
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!