Which reactions are single displacement reactions? 2nabr + caf2  → 2naf + cabr2sno2  + 2h2  → sn + 2h2o4na + o2  → 2na2o2kclo3  → 2kcl + 3o22al + 6hcl → 2alcl3  + 3h2

 The reactions that are   single  displacement reactions are

2SnO₂  +2 H₂  →  Sn  +2H₂O

2Al +6HCl    → 2AlCl₃  +3H₂

 Explanation

Single  displacement is type of chemical reaction  where  element  reacts  with compound  and take  the place   of another  element  in that compound

In  the  first  reaction,  H₂ displaces O₂  from SnO₂ to  form Sn and H₂O

In  second reaction Al element  displaces  H from HCl  to  form AlCl₃  and H₂

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)