Asap ! how to balance equations with brackets? like pb(no3)2? how many of each element is there?

Replace the formulas inside the parentheses with single letters  

Explanation:

Here's an equation with lots of parentheses.

(NH₄)₃PO₄ + Pb(NO₃)₂ ⟶ NH₄NO₃ + Pb₃(PO₄)₂

It looks impossible to balance, doesn't it?

One way to balance the equation is to recognize that the polyatomic ions (the formulas inside the parentheses) stay together.

Then we can make some substitutions.

Let A = NH₄, X = PO₄, and Y = NO₃

Then the equation becomes

A₃X + PbY₂ ⟶ AY + Pb₃X₂

Here's how to balance it.

1. Start with the most complicated formula, Pb₃X₂, and put a 1 in front of it.

A₃X + PbY₂ ⟶ AY + 1Pb₃X₂

2. Balance Pb

We have fixed three atoms of Pb on the right, so we need three atoms of Pb on the left. Put a 3 in front of PbY₂.

A₃X + 3PbY₂ ⟶ AY + 1Pb₃X₂

3. Balance X

We have fixed two atoms of X on the right, so we need two atoms of X on the left. Put a 2 in front of A₃X.

2A₃X + 3PbY₂ ⟶ AY + 1Pb₃X₂

4. Balance A

We have fixed 6 atoms of A on the left, so we need 6 atoms of A on the right. Put a 6 in front of AY.

2A₃X + 3PbY₂ ⟶ 6AY + 1Pb₃X₂

Every formula has a coefficient, and the equation is now balanced.

Next, we replace the original formulas in the equation.

The balanced equation is

2(NH₄)₃PO₄ + 3Pb(NO₃)₂ ⟶ 6NH₄NO₃ + 1Pb₃(PO₄)₂

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.

i have no clue hope you find the answer