Molality is defined as the number of moles of solute in 1 kg of solvent.
molality of solution to be prepared is 0.50 molal
this means that in 1000 g of water there should be 0.50 mol of NaCl
if 1000 g of water should contain - 0.50 mol
then 750.0 g of water requires - 0.50 mol/kg x 0.750 kg = 0.375 mol
mass of NaCl in 0.375 mol - 58.5 g/mol x 0.375 mol = 21.9 g
therefore a mass of 21.9 g of NaCl is required
Answer:
the specimen has 11460 years old
Explanation:
if the live sample has as initial amount of Yo C14, the dead sample will have 0.25Yo of C14.
the rate of decay of radiactive matter over time is
- Y(t) = Yo * e (( - t * Ln2 ) / T)
∴ Y(t) = 0.25Yo; T = 5730
⇒ 0.25Yo = Yo * e (( - t * Ln2 ) / 5730 )
⇒ 0.25 = e (( - t * Ln2 ) / 5730 )
⇒ Ln(0.25) = ( - t * Ln2 ) / 5730
⇒ - 7943.466 = - t * Ln2
⇒ 7943.466 / Ln2 = t
⇒ t = 11460 year
Answer:
Magnesium Nitrate is an ionic compound formed by:
Magnesium;Mg+2 (<em>the cation)</em> and Nitrate NO−3 (<em>the poly-atomic anion)</em>.
In order for these two ions to bond, the charges must be equal and opposite. Therefore, it will take:
<u>two -1 nitrate ions</u> <u>to balance the</u> <u>one +2 magnesium ion</u>.
Answer:
The sum of the number of protons and neutrons in an atom is called the mass number.
Explanation:
Carbon-12 has 12 protons and 12 neutrons. 12+12=24 , so the mass number of C-12 is 24..
Hope it helps..
