Question

out of 3 metals p,q,r p is less reactive than q and r is more reactive than p and q more suggest an activity to arrange p,q,r in order of the decreasing reactivity ​

Answer 1

Take the required salt solutions of p, q and r and make them reacting separately. You will observe p displaces it from all the compound thus proving that it is more reactive

For eg:p+qSo4->pSo4+q

Here q gets displaced as it is less reactive than the other ones. You can prove the rest similarly

Answer 2

Taking salt solution of metal P, metal Q and metal R. we know, when salt solution of a given metal is displaced by another metal then, reactivity of that metal is higher than metal present in salt. for example , salt of metal A + metal B → salt of metal B + metal A

then, reactivity of B > reactivity of A.

here, a/c to question,

P is less reactive than Q

so, Q > P .....(1)

it can be written as salt of metal P + metal Q → salt of metal Q + metal P

again, R is more reactive than P and Q both.

so, R > P and R > Q .......(2)

it can be written as

salt of metal P + metal R → salt of metal R + metal P

and salt of metal Q + metal R → salt of metal R + metal Q

from equations (1) and (2),

R > Q > P

hence, reactivity order is R > Q > P