Which sets of chemicals , when mixed , produce the observation (s) listed ?

Which one of the following pairs of substances when mixed, produces chlorine gas at room temperature?

Which of the following substances when mixed together will produce table salt ?

If the S.D. of a set of observations is 8 and if each observation is divided by -2, the S.D. of the new set of observations will be (a) -4 (b) -8 (c) 8 (d) 4

If the S.D. of a set of observations is 8 and if each observation is divided by -2, the S.D. of the new set of observations will be (a) -4 (b) -8 (c) 8 (d) 4

If the S.D. of a set of observations is 8 and if each observation is divided by -2, the S.D. of the new set of observations will be (a) -4 (b) -8 (c) 8 (d) 4

Which of the following salts will not produce any observable changes when H_(2)S is passed through its aqueous solution?