Answer:
We could do two 1:50 dilutions and one 1:4 dilutions.
Explanation:
Hi there!
A solution that is 1000 ug/ ml (or 1000 mg / l) is 1000 ppm.
Knowing that 1 ppm = 1000 ppb, 100 ppb is 0.1 ppm.
Then, we have to dilute the stock solution (1000 ppm / 0.1 ppm) 10000 times.
We could do two 1:50 dilutions and one 1:4 dilutions (50 · 50 · 4 = 10000). Since the first dilution is 1:50, you will use the smallest quantity of the stock solution (if we use the 10.00 ml flask):
First step (1:50 dilution):
Take 0.2 ml of the stock solution using the third dispenser (20 - 200 ul), and pour it in the 10.00 ml flask. Fill with water to the mark (concentration : 1000 ppm / 50 = 20 ppm).
Step 2 (1:50 dilution):
Take 0.2 ml of the solution made in step 1 and pour it in another 10.00 ml flask. Fill with water to the mark. Concentration 20 ppm/ 50 = 0.4 ppm)
Step 3 (1:4 dilution):
Take 2.5 ml of the solution made in step 3 (using the first dispenser 1 - 5 ml) and pour it in a 10.00 ml flask. Fill with water to the mark. Concentration 0.4 ppm / 4 = 0.1 ppm = 100 ppb.
Answer: 1.25 miles per minute
Explanation:
Average speed is the rate of change of total distance covered per unit time.
i.e Average speed = (Total distance / Time taken)
Total distance covered = (25miles + 40 miles + 70 miles + 15 miles)
= 150 miles
Total time taken = ( 15 minutes + 30 minutes + 1 hour + 15 minutes) = 120 minutes
Since 60 minutes = 1 hour, the total time taken is 120 minutes
Now, apply Average speed = (Total distance / Time taken)
= (150 miles / 120 minutes)
= 1.25 miles per minutes
Thus, Joseph drove with an average speed of 1.25 miles per minute.
Sorry if i’m late but your answer should be infrared
Answer:
D
Explanation:
The noble gases are said to be inert because they undergo very few chemical reactions. They enjoy their status by having completely filled electron shells and do not have any reason whatsoever to go into chemical reactions. Most elements otherwise go into chemical reactions principally to enjoy the stability of these elements.
Noble gases can be found in the last group of the periodic table.
