Answer:
16 minutes
Explanation:
First, we need to calculate the amount of heat needed to cool the beef stew:
Q = mcΔT
Where <em>m</em> is the mass, <em>c</em> is the heat capacity and <em>ΔT</em> is the variation of the temperature.
Q = 10x4x(40 - 90)
Q = -2000 kJ
So, the beef stew needs to lost 2000 kJ to cool.
With the initial temperature at 90ºC, the rate of cooling(r) will be:
r = 1.955x(90 - 25)
r = 127.075 kJ/min
So, to lose 2000 kJ, will be necessary:
t = Q/r
t = 2000/127.075
t = 16 minutes
Answer:
3.18 (w/w) %
Explanation:
In the problem, you can find mass of NaClO knowing the reaction of NaClO with Na₂S₂O₃ is:
NaClO + 2Na₂S₂O₃ + H₂O → NaCl + Na₂S₄O₆ +2NaOH + NaCl
<em>Where 1 mole of NaClO reacts with 2 moles of Na₂S₂O₃</em>
<em> </em>Moles of thiosulfate in the titration are:
0.0101L ₓ (0.042mol / L) = 4.242x10⁻⁴ moles of Na₂S₂O₃
Thus, moles of NaClO in the initial solution are:
4.242x10⁻⁴ moles of Na₂S₂O₃ ₓ (1mol NaClO / 2 mol Na₂S₂O₃) = 2.121x10⁻⁴ moles NaClO
As molar mass of NaClO is 74.44g/mol, mass of 2.121x10⁻⁴ moles are:
2.121x10⁻⁴ moles ₓ (74.44g / mol) = <em>0.0158g of NaClO</em>
As mass of bleach is 0.496g, mass percent is:
0.0158g NaClO / 0.496g bleach ₓ 100 =
<h3>3.18 (w/w) % </h3>
Answer: A. 490.48mol
Explanation:
Using the ideal gas equation; PV =nRT
where P = Presssure = 200 atm
V = Volume = 60L
n = Number of moles
R = Gas constant = 0.08206 L.atm/mol/K
T = Temperature = 25 °C + 273 = 298K
Make "n" the subject of the formular;
n = PV / RT
= 200 x 60 / 0.08206 x 298
= 490.73 mol, which is closest to option A. 490.48mol
Answer:
The molecular formula for aspartame is C14H18N2O5, and its molar mass is about 294 g/mol. 1.2 g / 294 g/mol = 4.08 X 10-3 moles aspartame. Since each mole of aspartame has 2 moles of nitrogen, you have 8.16 X 10-3 moles of N in your 1.2 grams of aspartame.
Explanation:
Significant figures are the digits that come after the first non-zero digit. The second value has 11 significant figures and is therefore the correct answer. However, the fourth answer has 4 significant figures and would also be a correct answer. So I don’t know if perhaps there has been a typo or a mistake in the question but with what you have provided here, both these answer have more than 2 significant figures.
