Answer:
after 45 days 9 g left
Explanation:
Given data:
Half life Na-24 = 15 days
Mass of sample = 72 g
Mass remain after 45 days = ?
Solution:
Number of half lives passed:
Number of half lives = time elapsed / half life
Number of half lives = 45 days / 15 days
Number of half lives = 3
At time zero total amount = 72 g
After first half life = 72 g/ 2= 36 g
At 2nd half life = 36 g/2 = 18 g
At 3rd half life = 18 g/2 = 9 g
Thus after 45 days 9 g left.
If Gold's natural state has a definite shape and a definite volume, then its natural state is solid.
Explanation:
Given that:
Distance traveled = 3150m
Average speed = 350m/min
Suggested speed = 375m/min
Unknown:
Time = ?
Solution:
Speed is the rate of change of distance with time.
it is mathematically expressed as;
speed = 
Initial time using speed 350m/min can be calculated by making time the subject of the formula;
time taken = 
time taken at speed of speed of 350m/min = 
= 9min
to seconds = 9 x 60 = 540 seconds
time taken at speed of 375m/min = 
= 8.4min
to seconds = 8.4 x 60 = 504 seconds.
It could have taken 504 seconds sooner saving 36 seconds.
learn more:
Speed brainly.com/question/10177389
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Answer:
SeF4 is a polar molecule
Explanation:
SeF4 is a polar molecule because a polar molecule is any molecule that have lone pairs of electrons in the central atom or have atoms that are electronegative and the electrons between that are covalently bonded are not evenly distributed.
The electronegative atoms of flourine in SeF4 are not evenly distributed and kind pairs of electrons are on the central atom.
B KOH
I would say this is the base for the compound substance
