Standard temperature is 273 K
Standard pressure is 1 atm
We use the ideal gas equation to find out density of nitrogen gas in g/L
Ideal gas equation:
Molar mass of 
Pressure = 1 atm
Temperature = 273 K
= 1.25 g/L
Therefore, density of nitrogen gas at STP is 1.25 g/L
D. Fish
The brain is part of an organism's central nervous system. Simpler organisms such as sponges, hydrae, and flatworms lack the complexity in their central nervous systems to have a brain. A fish, on the other hand, is complex enough to have a central brain.
Answer:
D. You can no longer tell if your original sample contained Na+ or K+.
Explanation:
Group reagents are the reagents which are used to separate a whole group of cations from the other groups of cations.
For example, for group 1 , the group reagent is HCl and for group 5, the group reagent is ammonium carbonate.
<u>When sodium chloride and potassium carbonate is used, it means we are contaminating our sample with foreign cations which may interfere in the process of detection. Also, we will not be able to decipher whether the sample has these ions in the initial or not as we have added them.</u>
