Choose all the answers that apply.

which of the following equations are balanced?

2h2 + o2 → 2h2o

2s + 3o2 → 2so3

li + cl2 → licl

2k + 2h2o → h2 + 2koh

2fe + cu(no3)2 → 2cu + fe(no3)2

Answer : The balanced chemical equations are:

Explanation :

Balanced chemical reaction : It is defined as the reaction in which the number of atoms of individual elements present on reactant side must be equal to the product side.

(1) The given chemical reaction is,

This reaction is a balanced chemical reaction because in this reaction the number of atoms of individual elements present on reactant side must be equal to the product side.

(2) The given chemical reaction is,

This reaction is a balanced chemical reaction because in this reaction the number of atoms of individual elements present on reactant side must be equal to the product side.

(3) The given chemical reaction is,

This reaction is an unbalanced chemical reaction because in this reaction the number of chlorine atoms are not balanced.

In order to balance the chemical equation, the coefficient '2' put before the and we get the balanced chemical equation.

The balanced chemical reaction will be,

(4) The given chemical reaction is,

This reaction is a balanced chemical reaction because in this reaction the number of atoms of individual elements present on reactant side must be equal to the product side.

(5) The given chemical reaction is,

This reaction is an unbalanced chemical reaction because in this reaction the number of iron and copper atoms are not balanced.

In order to balance the chemical equation, we are removing the coefficient '2' that present before and we get the balanced chemical equation.

The balanced chemical reaction will be,

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.