Enter your answer in the provided box. When mixed, solutions of barium chloride, BaCl2, and potassium chromate, K2CrO4, form a yellow precipitate of barium chromate, BaCrO4. The balanced equation is: BaCl2(aq) + K2CrO4(aq) → BaCrO4(s) + 2KCl(aq) How many grams of barium chromate are expected when a solution containing 0.70 mol BaCl2 is mixed with a solution containing 0.14 mol K2CrO4?

35.42g

Explanation:

Step 1:

The balanced equation for the reaction

BaCl2(aq) + K2CrO4(aq) → BaCrO4(s) + 2KCl(aq)

Step 2:

Determination of the limiting reactant.

It is important to determine which of the reactant is limiting the reaction as the limiting reactant is used to determine the maximum yield of the reaction. The limiting reactant can be determined as follow:

From the balanced equation above,

1 mole of BaCl2 reacted with 1 mole of K2CrO4.

Therefore, 0.7 mole of BaCl2 will also react with 0.7 mol of K2CrO4.

From the above illustration, we can see that it requires a higher amount of K2CrO4 to react with 0.7 mol of BaCl2. This simply means that K2CrO4 is the limiting reactant.

Step 3:

Determination of the number of mole of BaCrO4 produced from the reaction.

The limiting reactant is used in this case.

From the balanced equation above,

1 mole of K2CrO4 produced 1 mole of BaCrO4.

Therefore, 0.14 mole of K2CrO4 will also produce 0.14 mole of BaCrO4.

Step 4:

Converting 0.14 mole of BaCrO4 to grams.

This is illustrated below:

Molar Mass of BaCrO4 = 137 + 52 + (16x4) = 137 + 52 + 64 = 253g/mol

Number of mole BaCrO4 = 0.14 mole

Mass of BaCrO4 =?

Mass = number of mole x molar Mass

Mass of BaCrO4 = 0.14 x 253

Mass of BaCrO4 = 35.42g

Therefore, 35.42g of BaCrO4 is produced from the reaction.

explanation: it gains negative electrons, therefore becoming negatively charged. as charge cannot be created, nor destroyed, only transferred, this leaves the wool positive. now that they have opposite charges, the two items attract.

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.