Answer:
8 oxygen. 9 flourine. 10. Neon. 5 Boron
Answer: 0.0250
Explanation: 10 X 0.0750 = .75
.75 / 30 = 0.0250 M
A barometer measures atmospheric pressure.
Answer:
C.
Explanation:
If the students want to know at what percent of CO2 in the air the plant will grow at the fastest, then the percent of CO2 should be a different value for each plant in the table.
There are 2 tables that have different values for the CO2 - the tables in answer choices C and D.
Since the students only want to know how the amount of CO2 affects the plant, every other variable should remain constant.
The only answer choice that has a changing value for the percent of CO2 and a constant value for every other variable is C.
Answer:

Explanation:
The question will be easier to solve if we interpret it as, " How long will it take until one-fourth of a sample of the element remains,?"
The half-life of the element is the time it takes for half of it to decay.
After one half-life, half (50 %) of the original amount will remain.
After a second half-life, half of that amount (25 %) will remain, and so on.
We can construct a table as follows:

