Dobereiner's Triads

Q.

Johann Dobereiner classified elements in group of three elements called as

1. Diads

2. Trials

3. Triads

4. Trinity

Q.

$\mathrm{Na}=\frac{\mathrm{Li}+\mathrm{K}}{2}=\frac{7+39}{2}=\frac{46}{2}=23$ What is dobereiners law of triads explain with the help of one example of dobereiners.

Q.

Which of these triads could not be justified as Dobereiner’s triad?

1. Li, Na, K

2. Cl, Br, I

3. C, N, O

4. Ca, Sr, Ba

Q. According to Dobereiner's theory of triads, the mass of middle element was roughly the average of atomic masses of other two elements.

1. False
2. True

Q. follows Dobereiner's law of Triads.

1. Sr, Ba, Ca
2. Br, Cl, I
3. Cl, Br, I

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

Q.

If three elements X, Y and Z form a triad and atomic weights of X and Z are 9 and 40, respectively, then the atomic weight of an element Y is _____.

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.

Elements A, B, C forms Dobereiners triads. If atomic mass of element A is 7 and the atomic mass of element C is 39. Then atomic mass of element B is

1. 46

2. 23

3. 53

4. 11

Q. who was the first scientist to classify elements according to their properties

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.

Which of the following are isoelectronic species i.e., those having the same number of electrons?

Na⁺, K⁺, Mg²⁺, Ca²⁺, S^2–, Ar