A 250.0 mL sample of aqueous solution contains an unknown amount of dissolved NaBr. Excess aqueous Pb(NO3)2is then added to this solution and a precipitate forms.
A. If the mass of precipitate recovered was 3.006 grams, what was the molar concentration of Br–ions in the original solution?
B. What is the chemical formula of the precipitate?
C. Write the net ionic equation for this precipitation reaction.

A. 0.0655 mol/L.

B. PbBr2.

C. Pb2+(aq) + Br- --> PbBr2(s).

Explanation:

Balanced equation of the reaction:

Pb(NO3)2(aq) + 2NaBr(aq) --> PbBr2(s) + 2NaNO3(aq)

A.

Number of moles

PbBr2

Molar mass = 207 + (80*2)

= 367 g/mol.

Moles = mass/molar mass

= 3.006/367

= 0.00819 mol.

Since 2 moles of NaBr reacted to form 1 mole of PbBr2. Therefore, moles of NaBr = 2*0.00819

= 0.01638 moles of NaBr.

Since, the ionic equation is

NaBr(aq) --> Na+(aq) + Br-(aq)

Since 1 moles of NaBr dissociation in solution to give 1 mole of Br-

Therefore, molar concentration of Br-

= 0.0164/0.25 L

= 0.0655 mol/L.

B.

PbBr2

C.

Pb(NO3)2(aq)--> Pb2+(aq) + 2No3^2-(aq)

2NaBr(aq) --> 2Na+(aq) + 2Br-(aq)

Net ionic equation:

Pb2+(aq) + 2Br- --> PbBr2(s)

when—without warning—something provokes your anger, you may struggle not to succumb to it. since what typically makes you mad is feeling powerless in the face of what seems unfair, your anger is mostly an attempt at a “quick fix” to right the balance. it’s as though you’re raising a fist in protest, proclaiming that you’re not going to capitulate to such injustice.

there are, however, a multitude of problems related to this immediate, push-back reaction of anger. and probably the key one is that almost never does it resolve the issue that gave rise to it. such reactive anger is probably best understood as self-defeating. as david burns, the author of the seminal self- book feeling good, observes: if realistically, acting on your anger is to make any sense, it needs to meet two criteria—which, in almost every case, is frankly impossible. that is, your anger must:

be directed toward a person who has intentionally (and needlessly) behaved in a hurtful way toward you; and

be beneficial or advantageous to you (i.e., assist you in achieving a desired goal).

i think you’ll agree that only rarely can you claim that your anger is both warranted and , whether to yourself or the relationship.

so let me offer you a two-step alternative to abandoning your better judgment and giving in to the temptation of anger—one that should neutralize your anger in seconds. or, when you’re really angry, in minutes.

but keep in mind that you must really want to execute these steps, be sufficiently motivated to perform them. which means overcoming more unconscious resistance than you might ever have imagined. because there are many immediate “advantages” of anger that can interfere with your resolve, i’ll suggest a few of them that might interfere with your employing this powerful method to rid yourself of counter-productive anger.

explanation:

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.