Answer:
<em><u>Question 1.</u></em><em> → </em>The amount remained is 15.625 g after 5 half-lives (30 hours).
<u><em>Question 2. </em></u><em>→ </em>mass % of water =41.4 %
<u><em>Question 3. </em></u><em>→ </em>C. 64 grams.
Explanation:
<em><u>Question 1. </u></em>
It is known that the decay of isotopes and radioactive material obeys first order kinetics.
Also, it is clear that in first order decay the half-life time is independent of the initial concentration.
Thus, 30 hours represent (30/6) 5 half-lives.
500 g →(first 1/2 life) 250 g →(second 1/2 life) 125 g →(third 1/2 life) 62.5 g →(fourth 1/2 life) 31.25 g →(fifth 1/2 life) 15.625 g
So, The amount remained is 15.625 g after 5 half-lives (30 hours).
<u><em>Question 2.</em></u>
- The formula of Copper (II) Fluoride tetra hydrate is CuF₂.4H₂O.
- the molar mass of Copper (II) Fluoride tetra hydrate is the sum of the atomic masses o each element.
- molar mass of 1 mol of CuF₂.4H₂O = 64 + 2*(19) + 8* (1) + 4*(16) = 174 g/mol.
- molar mass of 4 mol of H₂O = 8*(1) + 4*(16) = 72 g/mol
- 1 mol of Copper (II) Fluoride tetra hydrate → 4 mol H₂O
mass % of water = (mass of 4 mol of H₂O) / (mass of 1 mol of CuF₂.4H₂O ) *100 = (72 /174) *100 = 41.4 %
<em><u>Question 3. </u></em>
<u>Mass percentage</u> is defined as the mass of a solute divided by the total mass of the solution, multiplied by 100
- mass percent = ( mass of solute / mass of solution) *100
∴ 16 = ( mass of solute / 400 g) *100
mass of solute = (16* 400)/ 100 = 64 g.
So the right choice is C. 64 grams.
Answer:
The correct answer is option e, that is, 1.65 * 10^-2.
Explanation:
Based on the given information, the weight of NaI given is 74.2 grams and the weight of water given is 527 grams.
The final volume of the solution given is 566 ml.
The formula to calculate the moles is weight/molecular mass,
The moles of NaI will be,
= 74.2/150 = 0.494
Now moles of water will be,
= 527/18 = 29.3
The mole fraction of NaI will be,
= 0.494 / (0.494 + 29.3)
= 0.0165 or 1.65 * 10^-2
Hence, the mole fraction of NaI is 1.65 * 10^-2
Answer:I beams can withstand greater Moment compared to other beams like rectangular beam when given the same stress.
Rectangular beams are better for casting concrete beams, and for making beams of high and low moment of inertia and its centriod is easy to understand.
Explanation: I beams are beams usually used in metal work and in making beams of high moments of inertia.
Rectangular beams are beams whose centroid ( the geometric center of a regular rectangular beam) are easily identifiable and they can be built to give high and low moment of inertia. This is one of the advantage of using rectangular beams.
The solution is buffered with a weak acid and it's conjugate base. Since NaOH is a base, you can use a weak acid as it's buffer.