Do you want to be a scientist or not because I can help you with that it's so easy
Answer:- 
molecules.
Solution:- The grams of tetrabromomethane are given and it asks to calculate the number of molecules.
It is a two step unit conversion problem. In the first step, grams are converted to moles on dividing the grams by molar mass.
In second step, the moles are converted to molecules on multiplying by Avogadro number.
Molar mass of 
= 12+4(79.9) = 331.6 g per mol
let's make the set up using dimensional analysis:
= molecules
So, there will be molecules in 250 grams of .
Answer:
halogens
Explanation:
on a periodic table (just search ptable.com) right under the 17 in small words it says halogens
Answer:
about 30g
Explanation:
Molarity = mol/L
*convert mL to L*
3M=xmol/.25
xmol = .75
*convert to g
.75 mol NaOH * 40g/mol = 30 g
It is a good thing that you already have answered the first question. Now, moving on to the second question, there exist an equation for the neutralization of acid by a base that is shown below,
M₁V₁ = M₂V₂
Now, all the variables in the equation are given except for our unknown which is the V₂. Substituting the known values from the given above,
(0.1 M)(25 mL) = (0.05 M)(V₂)
The value of V₂ from the equation above is 50 mL. Therefore, 50 mL of 0.05 M NaOH solution will be needed to completely react with HNO3.
