Dobereiner's Triads

Q.

Why the law of triads not applicable in C, N, O?

Q. Consider the coordination compound $\left[Co\right(Gly{)}_3]$.
If number of geometrical isomers is x and y is number of enantiomeric pairs possible, then value of $x^2+y^2$ is

Q. Which of the following is Dobereiner triad

1. Fe, Co, Ni
2. Ru, Rh, pd
3. Os, Ir, Pt
4. Li, Na, K

Q.

State one achievement of classification of elements by the Law of Triads.

Q. Dobereiner arranged similar elements in a group of three i.e. triads, on the basis of:

1. Similar physical and chemical properties
2. The atomic weight of the middle element was approximately the arithmetic mean of the other two elements
3. The atomic weight of the third element was approximately the arithmetic mean of the first two elements
4. Both (a) and (c)

Q. Identify the element 'X' from the dobernier triad given below:

Element	Chlorine (Cl)	X	Iodine (I)
Atomic Mass (A)	35.5	Y	126.9

1. X : Bromine
   Y : 82.0
2. X : Bromine
   A : 79.9
3. X : Fluorine
   Y : 82.0
4. X : Fluorine
   Y : 79.9

Q.

State two reasons for rejecting Triads classification of elements.

Q. The first attempt towards the classification of elements was made by:

1. John Alexander Newlands
2. Lothar Meyer
3. Wolfgang Dobereiner
4. Dmitri Ivanovich Mendeleev

Q. $H_{2}S$, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of $H_{2}S$ in water at STP is $0.195m$, calculate Henry's law constant.

Q.

Can the following groups of elements be classified as Dobereiners triad?

(a) Na, Si, Cl

(b) Be, Mg, Ca

The atomic mass of Be-9, Na-23, Mg-24, Si-28, Cl-35, and Ca-40 explain by giving a reason.

Q.

Atomic weights of three elements in a Doberenier triad are x, 81, and 127. Find the missing atomic weight.

1. 104

2. 35

3. 46

4. 23

Q. In a hypothetical universe, if atomic numbers were used to form triads, which of the following will make triad with Na and K:

1. P

2. Ca

3. Si

4. Mn

Q. Atomic mass of X and Z is 20 and 40 respectively. If X, Y and Z form a Dobereiner's triad then the value of Y is

1. 20
2. 30
3. 40

Q. Which of the following statement is not true about Doebereiner's Law of Triad?

1. The law was applicable to all known elements
2. Nitrogen family does not obey the law of triads
3. Doebereiner's classification was not very useful
4. The atomic mass of central element of each was merely the arithmetic mean of the atomic masses of other two elements.

Q.

Identify the set of three elements which can obey the Law of triads.

1. $\mathrm{Na},\mathrm{K},\mathrm{Rb}$

2. $\mathrm{Be},\mathrm{Mg},\mathrm{Ca}$

3. $\mathrm{F},\mathrm{Cl},\mathrm{Br}$

4. $\mathrm{C},\mathrm{Si},\mathrm{Ge}$

Q. The first attempt towards the classification of elements was made by:

1. John Alexander Newlands
2. Lothar Meyer
3. Wolfgang Dobereiner
4. Dmitri Ivanovich Mendeleev

Q. Dobereiner arranged similar elements in a group of three i.e. triads, on the basis of:

1. Similar physical and chemical properties
2. The atomic weight of the third element was approximately the arithmetic mean of the first two elements
3. Both (a) and (c)
4. The atomic weight of the middle element was approximately the arithmetic mean of the other two elements

Q. Dobereiner arranged similar elements in a group of three , i.e, triads, on the basis of?

1. Nearly the same atomic weight
2. The atomic weight of the third element was approximately the arithmetic mean of the first two elements
3. The atomic weight of the middle element was approximately the arithmetic mean of the other two elements
4. Both $\left(a\right)$ and $\left(c\right)$

Q. Chlorine, Y and Iodine form a Dobereiner's triad. Identify the atomic weight of Y.

1. 162.5
2. 121.5
3. 90.5
4. 81.25

Q.

Do law of triads applicable to C, N, O ?

Q. In a triad of $A,B,C$ elements, if the atomic masses of $A$ and $C$ respectively are $100$ and $200$, then the atomic mass of $B$ is:

1. $175$
2. $300$
3. $125$
4. $150$

Q. The mole fraction of ethanol in a solution of ethanol in water is $0.05$ and the density of solution is $0.997$ g/cc.
Which of the following statement(s) is/are correct?

1. Molality of the solution is $2.92m$
2. Molarity of the solution is $2.57M$
3. Molarity of the solution is $3.57M$
4. Molality of the solution is $3.52m$

Q.

The gram formula mass of $ZnS{O}_4$ is g.
(Given molar mass of $Zn$ in 65 g/mol)

Q. Which of the following elements follow Dobereiner's law of Triads?

1. Na = $23$, K = $39$ and Rb = $85$
2. Ca = $40$, Mg = $24$ and Sr = $88$
3. Cl = $35$, Br = $80$ and F = $19$
4. Na = $23$, Li = $7$ and K = $39$

Q.

Atomic mass of X and Z is 20 and 40 respectively. If X, Y and Z is Dobereiner's Triad. What can be the atomic number of Y?

1. 20

2. 40

3. 30

4. All of these

Q. Which of the following sets of atomic masses do not correspond to Dobernier traid?

1. $7,23,39$
2. $20,38,56$
3. $54,95,183$
4. $47,91,178$

Q. Which of the following statement is not true about Doebereiner's Law of Triad?

1. The law was applicable to all known elements
2. Nitrogen family does not obey the law of triads
3. Doebereiner's classification was not very useful
4. The atomic mass of central element of each was merely the arithmetic mean of the atomic masses of other two elements.

Q.

Identify the set of atomic numbers which does not obey the Dobereiners Law of triads.

1. $20,38,56$

2. $3,11,19$

3. $17,35,53$

4. $5,13,31$

Q. Who proposed the law of traids?

Q. Explain the laws of Dobereiner and Mendeleev for classification of elements?