3. A Group III unknown is analyzed with the following results. State which ions are present, absent or questionable. The ppt. obtained when H2S (thioacetamide) is added in basic solution is partially soluble in HCl. Treatment of the HCl solution with NaOH and NaClO gives a strongly colored solution and a ppt. that is partially soluble in H2SO4. (1) Fe+2/Fe+3 definitely present definitely absent questionable (1) Al+3 definitely present definitely absent questionable (1) Zn+2 definitely present definitely absent questionable (1) Mn+2 definitely present definitely absent questionable (1) Cr+3 definitely present definitely absent questionable (1) Co+2 definitely present definitely absent questionable (1) Ni+2 definitely present definitely absent questionable (1) Cd+2 definitely present definitely absent questionable

h let me think

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

i think its 100

i hope this !

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.