Answer:
radiation is measured using the conventional unit rad or the SI unit gray (Gy). The biological risk of exposure to radiation is measured using the conventional unit rem or the SI unit sievert (Sv).
Answer: 2800 g
Explanation:

According to avogadro's law, 1 mole of every substance weighs equal to molecular mass and contains avogadro's number
of particles.
Given mass = 5 kg = 5000 g
1 mole of
produces = 1 mole of 
50 moles of
produces =
of 
Mass of 
2800 g of
is produced from 5.0 kg of limestone.
Missing chemical reaction:
Pb(NO₃)₂(aq) + Li₂SO₄(aq) → PbSO₄(s) + LiNO₃(aq).
Answer is:
Balanced chemical reaction:
Pb(NO₃)₂(aq) + Li₂SO₄(aq) → PbSO₄(s) + 2LiNO₃(aq).
Number of atoms on both side of chemical reaction must be the same. There is two lithium atoms, two nitrogs, ten oxygen atoms, one lead and one sulfur on both side of balanced chemical reaction.
Answer:
Option B, When the cell needs to move a compound against its concentration gradient.
Explanation:
A cell uses active transport when it has to transport substances against the concentration gradient across its membrane.
In active transport additional energy is used (generally provided by energy molecules like ATP) to push the substance across any membrane from low concentration side to high concentration side.
Option B is correct
The measure of how much solute is mixed in with a solvent is called concentration. It's how much solute was put into the solvent (most likely water) <span />