What volume of a 6.84m sodium bromide solution would be needed to make 588ml of a 1.84m solution by dilution

Significant figures are digits read directly from the measuring instrument plus one more digit, which is __ by the observer.

Which factor is likely to impact the possible number of compounds ?

Given the following at 25c calculate delta hf for hcn (g) at 25c. 2nh3 (g) +3o2 (g) + 2ch4 (g) > 2hcn (g) + 6h2o (g) delta h rxn= -870.8 kj. delta hf=-80.3 kj/mol for nh3 (g), -74.6 kj/mol for ch4, and -241.8 kj/mol for h2o (g)