Answer:
36
Explanation:
Since the sample was undiluted the number of colonies is the number that grew on the nutrient agar which is 36 colonies. If it was diluted for example let say 0.1 ml from a dilution in which 1 ml of the sample was added to 9 ml of water, and it grew colonies then 0.1 ml yielded 6 colonies, 1 ml of the diluted sample will yield 60 colonies and 10 ml will have 600 colonies and therefore the 1 ml undiluted sample will have 600 colonies.
Explanation:
Half life is simply the amount of time it takes for half of a substance to decompose.
Options;
- Carbon-14 has a half-life of 5,730 years. A 30 gram sample will be 10 grams after 5,730 years. This is incorrect. After 5730 years, 15g of the sample ought to remain.
- Nickel-59 has a half-life of 76,000 years. A sample would go through 3 half-lives in 228,000 years. This is correct. 3 * 76000 = 228,000
- Hafnium-182 has a half-life of 9 million years. A 38 gram sample would be 4.75 grams in 27 million years. This is incorrect. Mass after 3 half lives (27/9) = 9.5 (38 / 2 / 2)
- Iron-60 has a half-life of 1.5 million years. In 6 million years a 40 gram sample would be reduced to 10 grams. This is incorrect. Mass after 4 half lives (6 / 1.5) = 2.5 gram (40 / 2 / 2 /2 / 2)
- Lead-202 has a half-life of 52,500 years. The original sample must have been 120 grams if you have a 60 gram sample after 105,000 years. This is incorrect. Original sampe = 240 gram. So after 2 half lives (105,000/52500), mass left = 60 (240 / 2 /2)
Answer: Option B
Explanation:
Dead space is the volume of sir in the body which is inhaled but it does not takes part in the gaseous exchange this is because it does not contains alveoli.
Not all the air that is inhaled inside the body is used in the process of respiration.
The dead space in the lungs is the region which helps in conducting airways, the air is not perfused to the alveoli.
Answer:
1. When you see the moon, think of the whereabouts of the sun
2. The moon rises in the east and sets in the west, each and every day
3. The moon takes about a month (one month) to orbit the Earth
4. The moon’s orbital motion is toward the east
Explanation:
Answer:
15.71g
Explanation:
The general combustion equation for all hydrocarbons is
CxHy + (x+y/4) O2 = xCO2 + (y/2) H2O
For octane, C8H18 :
C8H18 + ( 8 + 18/4 ) O2 = 8CO2 + 9H2O
C8H18 + 50/4 O2 = 8CO2 + 9H2O
C8H18 + 25/2 O2 = 8CO2 + 9H2O
2C8H18 + 25 O2 = 16 CO2 + 18H2O (balanced)
From the balanced equation,
2 x 22.4 L of octane produced 16 [ 12 + (16 x 2)] of carbon dioxide
That is,
44.8 L of octane produced 704g of carbon dioxide
So, 1L of octane will produce 1 L x 704g/44.8 L = 15.71g of carbon dioxide
Therefore, 15.71g of carbon dioxide will be produced by the complete combustion of 1 L of octane.
