Answer:
0.0468 g.
Explanation:
- The decay of radioactive elements obeys first-order kinetics.
- For a first-order reaction: k = ln2/(t1/2) = 0.693/(t1/2).
Where, k is the rate constant of the reaction.
t1/2 is the half-life time of the reaction (t1/2 = 1620 years).
∴ k = ln2/(t1/2) = 0.693/(1620 years) = 4.28 x 10⁻⁴ year⁻¹.
- For first-order reaction: <em>kt = lna/(a-x).</em>
where, k is the rate constant of the reaction (k = 4.28 x 10⁻⁴ year⁻¹).
t is the time of the reaction (t = t1/2 x 8 = 1620 years x 8 = 12960 year).
a is the initial concentration (a = 12.0 g).
(a-x) is the remaining concentration.
∴ kt = lna/(a-x)
(4.28 x 10⁻⁴ year⁻¹)(12960 year) = ln(12)/(a-x).
5.54688 = ln(12)/(a-x).
Taking e for the both sides:
256.34 = (12)/(a-x).
<em>∴ (a-x) = 12/256.34 = 0.0468 g.</em>
Answer:
157.79 g
Explanation:
The definition of molality is:
- molality = moles of solute / kilogram of solvent
This means that in a 2.7 molal solution, there are 2.7 moles of NaCl per kilogram of water.
So now w<u>e convert those 2.7 moles of NaCl to grams</u>, using its <em>molar mass</em>:
- 2.7 mol * 58.44 g/mol = 157.79 g
Answer: The diagrams show gases that are stored in two separate but similar containers. If both gases are at the same temperature, which one has the greater pressure? Gas 2 because it has more particles that are colliding.
Explanation:
Answer:
Mass of aluminium in sample = 3.591 g ≅ 3.6 grams
Explanation:
Given that, A sample of aluminum absorbs 50.1 J of heat, upon which the temperature of the sample increases from 20.0°C to 35.5°C.
the specific heat of aluminum is 0.900 J/g- °C
The relation between heat absorbed and change in temperature is given by, Q = msΔT.
where Q = heat absorbed
m = mass of the substance
s = specific heat of substance
ΔT = change in temperature
Now, in our case, Q = 50.1 J ; s = 0.900 J/g- °C; ΔT= 35.5-20 = 15.5°C
⇒ m = 
⇒ m = 
= 3.591 g ≅ 3.6 g
⇒ m ≅ 3.6 g
