CHEMISTRY HIGH SCHOOL

Determine the freezing point of an aqueous solution containing 10.50 g of magnesium bromide in 200.0 g of water.

Answers

Answer 1
Answer: For an aqueous solution of MgBr2, a freezing point depression occurs due to the rules of colligative properties. Since MgBr2 is an ionic compound, it acts a strong electrolyte; thus, dissociating completely in an aqueous solution. For the equation:

                                ΔTf = (Kf)(m)(i)
where: 
ΔTf = change in freezing point = (Ti - Tf)
Ti = freezing point of pure water = 0 celsius
Tf = freezing point of water with solute = ?
Kf = freezing point depression constant = 1.86 celsius-kg/mole (for water)
m = molality of solution (mol solute/kg solvent) = ?
i = ions in solution = 3

Computing for molality:
Molar mass of MgBr2 = 184.113 g/mol

m = 10.5g MgBr2 / 184.113/ 0.2 kg water = 0.285 mol/kg


For the problem, 
ΔTf = (Kf)(m)(i) = 1.86(0.285)(3) = 1.59 = Ti - Tf = 0 - Tf

Tf = -1.59 celsius

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A fruit and oatmeal bar contains 142 nutritional calories. Convert this energy to calories

Answers

Answer is: a fruit and oatmeal bar contains 142000 calories.
A nutritional calorie, or kilocalorie, is equal to 1000 calories.
E = 142 kcal · 1000 cal/kcal.
E = 142 000 cal.
Calorie (cal), or small calorie, is the amount of energy needed to heat one gram of water by one degree Celsius.
One small calorie is approximately 4.2 joules.
A calorie is a unit of energy.

Final answer:

142 nutritional calories (Cal) are equal to 142,000 calories (cal) since one nutritional Calorie is equivalent to 1000 scientific calories (cal).

Explanation:

To convert 142 nutritional calories to calories, you need to understand the relationship between the two units. In nutrition, when we say 'calories', we actually mean 'kilocalories' (kcal). One nutritional calorie (with an uppercase C) is equal to one kilocalorie (kcal), and one kilocalorie is equivalent to 1000 calories (with lowercase c).

Therefore, 142 nutritional calories (Cal) are equivalent to 142,000 calories (cal).

The conversion formula is as follows:
142 Cal * 1000 = 142,000 cal

Draw and name all the isomers of the alkene C4H8

Answers

....H....H....H....H
....|.....|…..|…..|
H-C==C----C----C-H
.....….....…..|.....|
.................H.....H
butan-1-ene/butene/but-1-ene

....H....H....H....H
....|.....|…..|…..|
H-C----C==C----C-H
....|….....…........|
....H..................H
butan-2-ene/but-2-ene
These are the structural isomers of butene.The geometric isomers include trans-but-2-ene and cis-but-2-ene.
HOPE THIS HELPS *WINK*

Consider the hydrocarbon below. 2 carbons are double-bonded to each other; the pair are single bonded to H above left, above right, below right, and below left. What is the name of this hydrocarbon?

Answers

Answer:

Ethene.

Explanation:

To know the name of the compound given above, we must:

1. Determine the number of carbon present in the compound.

2. Determine whether a single, double or triple is present in the compound.

3. Combine the above to get the name.

Now, let us name compound given above. This is illustrated below:

1. The compound contains two (2) carbon atom.

2. The compound contains a double bond. Therefore, the compound is an alkene.

3. An alkene with two carbon atoms is called ethene.

Therefore, the name of the compound given in the question is called ethene.

Answer:

other guy is right :)

Explanation:

if you look up "ethene hydrocarbon" online, the image attached in the question pops up!

Which method can be used to make a reliable guess that a victim was under 17 years old?A) look for flat-bladed incisors
B) look for presence or absence of wisdom teeth
C) multiply the internal distance in centimeters between the coronoid processes by the external distance in centimeters between the jaw angles(mandibular angles)
D) look for shovel shaped incisors
(It's not C)

Answers

Answer:

B) look for presence or absence of wisdom teeth

Explanation:

The only way to make a reliable guess if a victim was under 17 years old is by looking if he already had the wisdom teeth, this teeth are located in the back of the mouth, and are the third molars that humans develop after the age of 17 or 18 years on average, some could develop them after.
B-Look for the presence or absenceof wisdom teeth

Which fraction of a Sr-20 sample remains unchanged after 87.3 years?

Answers

First off there are some issues in your questions but I can still help in answering this type of problem. First, there is no Sr-20. The 4 abundant form includes Sr-84, Sr-88, Sr-87, Sr-86, Sr-84. 
More importantly, the half life of strontium must be given. 

For demonstration sake, let us assume Sr-85 is the isotope. It has a half-life of 64.853 days and I'm assuming the units of 87.3 is in days. 

A/Ao = e^-(ln2/t)T

where A- final amount Ao -initial amount t- halflife T-total time elapsed

% = e^-(ln2/64.853)(87.3) = 0.3933 or 39.33%

What is the oxidation number of chlorine in HClO4?

Answers

CIO4-=-1

CI=4O=-1

O has a 2- oxidation change so

CI+4(-2)=-1

CI+(-8)=-1

CI=-1+8=7

So the oxidation number of chlorine is 7 in this case
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