An alloy consists of rubidium and one of the other alkali metals. A sample of `4.6g` of the alloy when allowed to react with water, liberates `2.241dm^(3)` of hydrogen at `STP`. Relative atomic masses: `A_(T)(Li)=7,A_(T)(Na)=23,A_(T)(K)=39,A_(T)(Rb)=85.5,A_(T)(Cs)=1.33` Which alkali metal is the component of the alloy?
Text Solution
Verified by Experts
The correct Answer is:
`M-alkali metal Reaction:`2M+2H_(2)Orarr2MOH+H_(2)` `n(H_(2)):0.1`mol `n(M):0.2`mol Mean molar mass: `M=(4.6g)/(0.2mol)=23gmol^(-1)`
An alloy consists of rubidium and one of the other alkali metals. A sample of 4.6g of the alloy when allowed to react with water, liberates 2.241dm^(3) of hydrogen at STP . Relative atomic masses: A_(T)(Li)=7,A_(T)(Na)=23,A_(T)(K)=39,A_(T)(Rb)=85.5,A_(T)(Cs)=1.33 What composition in % by mass has the alloy?
An experimenter is inside a uniformly accelerated train. Train is moving horizontally with constant acceleration a_(0) . He places a wooden plank AB in horizontal position with end A pointing towards the engine of the train. A block is released at end A of the plank and it reaches end B in time t_(1) . The same plank is placed at an inclination of 45^(@) to the horizontal. When the block is released at A it now climbs to B in time t_(2) . It was found that (t_(2))/(t_(1))= 2^((5)/(4)) . What is the coefficient of friction between the block and the plank?
a. If the velocity of a body is zero, does it mean that its acceleration is also zero ? (Yes//No) b. If the acceleration of a body is zero does it mean that its velocity is also zero ? (Yes//No) c. If a body travels with uniform acceleration a_(1) for a time t_(2) thenthe average acceleration is given by a_(av) =(a_(1)t_(1)+a_(2)t_(2))/(t_(1)+t_(2) (Yes//No) d. If a body starts from rest and moves with uniform acceleration the displacemects of the body is 1 s , 2 s, 3 s , etc., are in the ration of (1: 4: 9), etc. (True//False) e. For a body moving whith uniform acceleration, the displacent of the bosy in successive seconds is in the ration of 1: 3: 5: 7 .........................(True//False) .
Answer the following: a. Which of the following has density greater than water ? Li, Na, K, Cs . b. Arrange K, Li, Rb in other of increasing electrode potential. c. Arrange Na, Li, K and Cs in increasing order of metallic bond. d. Which among Na, K, Cs and Li forms stable hydride ? e. On reacting eith oxygen, potassium can form K_(2)O , KO_(2) and K_(2)O_(2) . Is it correct ? f. Give the name of the hardest alakli metal. g. Arrange the following in order orf increasing polarising albility. Li^(o+), Na^(o+), K^(o+), Cs^(o+) h. Mention some of the properties of alkali metals which increse down the group. i. Mention some of the properties of alkali metals which decrease down the group.
