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ch4aika [34]
2 years ago
14

Why did Mendeleev leave blank spaces in his version of the periodic table? Mendeleev’s periodic table arranged elements in order

of increasing atomic mass; spaces were left for elements not having the correct atomic mass. Mendeleev’s periodic table arranged elements in groups of similar chemical properties; spaces were left for elements not having a similar chemical property. Mendeleev’s periodic table arranged elements in order of increasing atomic mass; it was noticed that chemical properties repeated. Mendeleev predicted an element had not been discovered to fit the space.
Chemistry
2 answers:
mart [117]2 years ago
5 0

Answer:

Mendeleev’s periodic table arranged elements in order of increasing atomic mass; it was noticed that chemical properties repeated. Mendeleev predicted an element had not been discovered to fit the space.

Explanation:

on edge

mrs_skeptik [129]2 years ago
3 0

The answer is Mendeleev’s periodic table arranged elements in order of increasing atomic mass; it was noticed that chemical properties repeated. Mendeleev predicted an element had not been discovered to fit the space.

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A cell was set up having the following reaction Mg(s) + Cd2+ (aq) → Mg2+ (aq) + Cd (s) E°cell = 1.97 V The Magnesium electrode w
aliina [53]

Answer : The concentration of unknown Cd^{2+} will be, 1.807\times 10^{-6}M

Solution :

The balanced cell reaction will be,  

Mg(s)+Cd^{2+}(aq)\rightarrow Mg^{2+}(aq)+Cd(s)

Here magnesium (Mg) undergoes oxidation by loss of electrons, thus act as anode. Cadmium (Cd) undergoes reduction by gain of electrons and thus act as cathode.

Now we have to calculate the concentration of unknown Cd^{2+}.

Using Nernest equation :

E_{cell}=E^o_{cell}-\frac{0.0592}{n}\log \frac{[Mg^{2+}]}{[Cd^{2+}]}

where,

n = number of electrons in oxidation-reduction reaction = 2

E_{cell} = emf of the cell = 1.80 V

E^o_{cell} = standard cell potential = 1.97 V

[Mg^{2+}] = concentration of magnesium ion = 1.00 M

[Cd^{2+}] = concentration of cadmium ion = ?

Now put all the given values in the above equation, we get

concentration of unknown Cd^{2+}.

1.80=1.97-\frac{0.0592}{2}\log \frac{(1.00)}{[Cd^{2+}]}

[Cd^{2+}]=1.807\times 10^{-6}M

Therefore, the concentration of unknown Cd^{2+} will be, 1.807\times 10^{-6}M

6 0
2 years ago
. A mixture of methane and air is capable of being ignited only if the mole percent of methane is between 5% and 15%. A mixture
postnew [5]

Answer:

A) Mass flow rate of air = 22.892 kmol/hr

B)percentage by mass of oxygen in the product gas = 22.52%

Explanation:

We are given that the mixture containing 9.0 mole% methane in air flowing.

Thus, we have 0.09 mole of methane(CH4) and the remaining will be the air which is (100% - 9%) = 91% = 0.91

Molar mass of CH4 = 12 + 1(4) = 16 g/mol

We are given the average molecular weight of air = 29 g/mol

Thus;

Average molar mass of air and methane mixture is;

M_avg = (0.09 × 16) + (0.91 × 29)

M_avg = 27.83 g/mol

We are told that air flowing at a rate of 7 × 10² kg/h = 700 kg/h

Thus;

Mass flow rate of CH4 in air mixture = 700kg/h × (0.09CH4)/1 mix × (1/27.83kg/kmol) = 2.264 kmol/hr

Mass flow rate of air in mixture = 2.264kmol/h × 0.91kmol air/0.09kmolCH4 = 22.892 kmol/hr

We are told that the mixture is capable of being ignited if the mole percent of methane is between 5% and 15%.

Thus, for 5% of methane, the air required will be;

2.264kmol/h × 0.95kmol air/0.05kmol CH4 = 43.016 kmol/hr

Now, the dilution air needed will be =

43.016 - 22.892 = 20.124 kmol/hr

Total mass flow rate of mixture =

700kg/hr + (20.124kmol/hr × 29kg/mol) = 1283.596 kg/hr

We are told that air consist of 21 mole% Oxygen (O2).

Molar mass of oxygen = 32

Thus;

Mass fraction of oxygen in the product gas = 43.016kmol/h × (0.21molO2/1mol air) × (32kg oxygen/1kmol oxygen) × (1/1283.596kg/h) = 0.2252

Thus, written in percentage form, we have; 22.52%

So, percentage by mass of oxygen in the product gas = 22.52%

3 0
2 years ago
A solution contains one or more of the following ions: Ag + , Ca 2 + , and Co 2 + . Ag+, Ca2+, and Co2+. Lithium bromide is adde
Eva8 [605]

Answer:

Since with LiBr no precipitation takes place. So, Ag+ is absent

When we add Li2SO4 to it, precipitation takes place.

Ca2+(aq) + SO42-(aq) ----> CaSO4(s) ...Precipitate

Thus, Ca2+ is present.

When Li3PO4 is added, again precipitation takes place.Reaction is:

Co2+(aq) + PO43-(aq)---->Co3(PO4)2(s) ... Precipitate

A. Ca2+ and Co2+ are present in solution

B. Ca2+(aq) + SO42-(aq) ----> CaSO4(s)

C. 3Co2+(aq) + 2PO43-(aq)---->Co3(PO4)2(s)

8 0
2 years ago
The chlorination of methane occurs in a number of steps that results in the formation of chloromethane and hydrogen chloride. Th
kenny6666 [7]

Answer:

Total pressure = 0,806 atm

Partial pressure of CH₄: 0,037 atm

Partial pressure of Cl₂: 0,396 atm

Partial pressure of CH₃Cl: 0,125 atm

Partial pressure of HCl: 0,125 atm

Partial pressure of Cl⁻: 0,125 atm

Explanation:

For the reaction:

2CH₄(g)+3Cl₂(g)⟶2CH₃Cl(g)+2HCl(g)+2Cl⁻(g)

295 mL≡ 0,295L of methane at STP are:

n = PV/RT

P = 1 atm; V = 0,295L; R = 0,082atmL/molK; T = 273K.

moles of methane: 0,0132 moles

For 725 mL of chlorine ≡ 0,725L

moles of chlorine at STP are: ≡ 0,0324 moles

For a complete reaction of 0,0132 moles of CH₄:

0,0132 mol CH₄× \frac{3molCl_{2}}{2 molCH_{4}} = <em>0,0198 moles</em>

The reaction reaches 77%, moles of Cl₂ that react are: 0,0198×77% = 0,0153 mol

As you have 0,0324 moles of Cl₂, moles that will not react are:

0,0324 - 0,0153 = <em>0,0171 mol Cl₂</em>

As the reaction reaches 77% completion, moles of CH₄ that react are:

0,0132×77% =<em> 0,0102 moles of CH₄ And the moles that don't react are </em><em>0,00300 mol</em>

Thus, moles of each compound are:

0,0102 moles of CH₄×\frac{3Cl_{2}}{2 molCH_{4}}= <em>0,0153 mol  + 0,0171 mol = 0,0324 mol Cl₂</em>

0,0102 moles of CH₄×\frac{2CH_{3}Cl}{2 molCH_{4}}= <em>0,0102 mol CH₄</em>

0,0102 moles of CH₄×\frac{2HCl}{2 molCH_{4}}= <em>0,0102 mol HCl</em>

0,0102 moles of CH₄×\frac{2Cl^{-}}{2 molCH_{4}}= <em>0,0102 mol Cl⁻</em>

Total pressure using:

P = nRT/V

Where: n = 0,0102mol×3+0,0324mol + 0,0030mol = 0,0660mol; R = 0,082 atmL/molK; T = 298K; V = 2L

Total pressure = 0,806 atm

Partial pressure of CH₄: 0,037 atm

Partial pressure of Cl₂: 0,396 atm

Partial pressure of CH₃Cl: 0,125 atm

Partial pressure of HCl: 0,125 atm

Partial pressure of Cl⁻: 0,125 atm

<em>-To obtain partial pressure you change the moles for each compound-</em>

<em />

I hope it helps!

5 0
2 years ago
A gas has a pressure of 3.16 atm at STP. I have decided to transfer it to a container that is 3 times larger than the original v
Maru [420]

Answer: The new pressure will be 1.1atm

Explanation:

V1 = V

P1 = 3.16atm

V2 = 3V

P2=?

P1V1 =P2V2

3.16 x V = P2 x 3V

P2 = (3.16 x V) /3V

P2 = 1.1atm

7 0
2 years ago
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