Answer: A
Explanation: Beta particles have a charge of -1
Step 
<u>find the mass of a single washer</u>
Divide the total mass by the number of washers


Step 
<u>Convert kg to mg</u>
we know that

so

therefore
<u>the answer is</u>

The answer is (4) Ag(s)
Solid Silver has a Face Centered Cubic crystal structure.
The remaining choices are gases (H2 & Ar) and liquid (Br). Liquids and gases do not form crystal structures as their atoms are loose.
Answer:
20 mol
Explanation:
First, balance the chemical reaction
C3H8 + 5O2 --> 4H2O + 3CO2
Using the mole ratio, we can multiply the moles of propane by 4 to find the moles of H2O.
5 × 4= 20
20 mol