CHEMISTRY HIGH SCHOOL

The empirical formula for a compound is CH2. If n is a whole number, which shows a correct relationship between the molecular formula and the empirical formula? a)<br /><br /> empirical formula mass / molecular mass = n<br /><br /> B) molecular mass = element mass / empirical formula mass ´ 100<br /><br /> c) subscript of H in empirical formula = 2  subscript of H in molecular formula<br /><br /> D) subscript of C in molecular formula = n  subscript of C in empirical formula<br /><br />

Answers

Answer 1
Answer: An empirical formula is the "reduced" version of a molecular formula. For example, CH3 is the empirical formula for C2H6, C3H9, C4H12, and so forth. The difference in subscripts between an empirical formula and molecular formula is given by the constant n. If n is a whole number, this means the numerator is the molecular formula. So the answer is D. subscript of C in molecular formula = n  subscript of C in empirical formula. This can be rewritten as:

n = subscript of C in molecular formula/subscript of C in empirical formula
Answer 2
Answer:

Answer:

D

Explanation:

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When farmers irrigate their crops, as much as 60 to 70 percent of the water _____. is ruined by pests, such as rabbits that are around the crops never reaches the crop is taken up by the plant is already contaminated by lead pipes

Answers

Answer:

Option (2)

Explanation:

The water in most of the region is generally pumped out of the ground for the purpose of irrigation. This rate of pumping is much higher than the rate of replenishment. The over-pumping of water leads to the lowering of the water table

About 60 to 70% of the water that is used for irrigation purposes does not reach the crop. It is because the water most of the time gets percolated down into the deeper zones. In addition to this, the water also leaks through the fractures that are associated with the canals and increasing rate of evaporation.

Thus, the correct answer is option (2).

Answer:b never reaches the crop hopefully helps

Explanation:

David kept 100 grams of radioactive sodium in a container. He observed the amount of sodium left in the container after regular intervals of time and recorded them in the table shown below.Time (hours) Amount of sodium in container (in grams)
0 100
15 50
30 25
45 12.5

Based on the observations, which of these is most likely David's inference?
A.The half life period of radioactive sodium is 15 hours.
B.The half life period of radioactive sodium is 50 hours.
C.The amount of sodium left in the container after 60 hours will be 10.5 grams.
D.The amount of sodium left in the container after 60 hours will be 1.5 grams.

Answers

First we have to understand what a half life is. A half life is a measure of time when the amount of a certain object is 50% of the original amount. Hence the answer for this is letter A. The initial amount is 100. fifty percent of 100 is 50 and that happens after 15 hours. Hence, 15 hours is the half life period. 

Answer: A. The half life period of radioactive sodium is 15 hours.

Explanation:

Half life is the time taken by a reactant to reduce to its original concentration. It is designated by the symbol t_(1)/(2).

Given:

At 0 hours the amount of sodium in container is 100 grams

After 15 hours , the amount of sodium in container is 50 grams which is half of the original amount of 100 grams.

It will take 15 hours for half of a 100 g sample to decay to half of the amount i.e. 50 grams.

Which molecule has a tetrahedral arrangement of electron pairs but is not a tetrahedral molecule?

Answers

The answer is water H2O

The correct answer is

Water

:)

Tetrachloromethane, CCl4, is classified as a(1) compound because the atoms of the elements are combined in a fixed proportion
(2) compound because the atoms of the elements are combined in a proportion that varies
(3) mixture because the atoms of the elements are combined in a fixed proportion
(4) mixture because the atoms of the elements are combined in a proportion that varies

Answers

Correct Answer: compound because the atoms of the elements are combined in a fixed proportion.

Reason:
A  chemical compound is a chemical substance composed of element (of same or different type) that are bonded in a fixed proportion. Depending upon the type of element, bond can be ionic or covalent. In present case, tetrachloromethane i.e. CCl4 has one 'C' atom that is covalently bonded to four 'Cl' atoms. 
Tetrachloromethane, CCI4, is classified as a compound because the atoms of the elements are combined in a fixed proportion.

MATCH THE FOLLOWING!!!(match each instrument with its description)

1. weather maps/satellite
2. Doppler radar
3. radiosonde
4. wind vane
5. psychrometer
__________________________________________________________________________
A. uses two thermometers; a dry and wet bulb
B. points in the direction winds are coming from
C. uses frequency waves to track particle movement
D. used to help track air masses and fronts
E. carried with a weather balloon

Answers

Answer: The correct matching sequence is:

1 -D , 2-C, 3-E, 4-B , 5-A

Explanation:

Weather maps/satellite:These are the satellites used to monitor the climate on the Earth in day and night.Like moc=vment of clouds, El Nino. La Nina ertc

Doppler radar  is a system used to track the velocity or motion of the rain , storm or precipitation.It emit microwave signals to check the change in frequency of the wave due to the motion of the particles.

Radiosonde is an instrument carried away by balloon or any other means into different layers of atmosphere and sends information via radio.

Wind vane is an instrument used to show the direction of the wind. P

Psychrometer  is an instrument used to measure atmospheric humidity.It consist of two thermometer that is wet bulb thermometer and dry bulb thermometer.

Match each weather instrument with its description.

  1. weather maps/satellite - used to help track air masses and fronts
  2. Doppler radar - uses frequency waves to track particle movement
  3. radiosonde - carried with a weather balloon
  4. wind vane - points in the direction winds are coming from
  5. psychrometer - uses two thermometers; a dry and wet bulb

What is the term used to describe the energy needed to get a reaction started?a. adhesion energy
c. cohesion energy
b. activation energy
d. chemical energy

Answers

When a reaction starts, activation energy is needed. 

Answer: b. activation energy
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