.150 = 3
20.20 = 4
25.00 = 4
If a 0 does not have a number or a period after it, it is not significant.
If the 0 is behind the decimal point, it is always significant.
Answer:

Explanation:
Using Gay Lusaac's law where there is no change in Volume. The pressure changes directly proportional to absolute T°
P₁/T₁ = P₂/T₂
P₁T₂/T₁
P₂ = 
P₂ = 
Answer:
416.876
Explanation:
Uhmm I am so so very sorry if this is incorrect
Answer:
Na^+
Explanation:
The symbol for sodium is Na. The term "sodium ion" assumes that the reader knows that sodium's single 3s electron is susceptible to theft by any nearby element that has a high electron affinity. Sodium's ionization energy is low, allowing the 3s electron to move elsewhere and leave behinf a positively charged Na^+ atom.