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3 years ago

Which of the following is a radioisotope used to date rock formations older than 50,000 years old?

1 answer:

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<span>The radioisotope used to date rock formations 50 000 years ago is Uranium. This radioactive uranium isotope having a mass number of 235 and its symbol is U, its atomic number is 92, and the mass number is 238, comprising 0.715 percent of natural uranium. When bombarded with neutrons it undergoes fission with the release of energy.</span>

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Dissolving 5.28 g of an impure sample of calcium carbonate in hydrochloric acid produced 1.14 l of carbon dioxide at 20.0 Â°c an

kvv77 [185]

Answer:

Percentage by mass of calcium carbonate in the sample is 93.58%.

Explanation:

Assumptions:

calcium carbonate was dissolved completely and the amount of carbon dioxide released was proportional to the amount of calcium carbonate.
the sample did not contain any other compound that released or reacted with carbon dioxide.

$PV = nRT$

$n = \frac{PV}{RT}$

$P = 791 mmHg = \frac{791 mmHg}{760 mmHg} x 1 atm = 1.040789 atm.$

$R = 8.314 \frac{J}{K*mol} = 0.082 \frac{L*atm}{K*mol}$

$T = 20^{0}C + 273^{0} C = 293 K$

$n = \frac{1.040789 atm * 1.14 L}{0.082 \frac{L * atm}{K * mol} * 293 K }$

$n = 0.0493839 mol.$

given the equation of the reaction:

$CaCO_{3} + 2HCL = CaCl_{2} + CO_{2} + H_{2}O$

from assumption:

amount carbon dioxide = amount of calcium carbonate

$n(CaCO_{3} ) = n(CO_{2} )$

reacting mass ( m ) = Molar Mass ( M ) * Amount ( n )

$m(CaCO_{3} ) = n(CaCO_{3} ) * M(CaCO_{3} )$

m = 0.04938397 $mol$ * 100 $\frac{g}{mol}$ = 4.93839 $g$

percentage by mass of CaC $O_{3}$ = $\frac{mass of pure }{mass of impure}*100 = \frac{4.93839g}{5.28g}*100 = 93.5802%$ .

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3 years ago

Rank the following compounds in order of decreasing magnitude of the lattice energy (most negative first). CsCl CaS LiCl

NemiM [27]

Answer:

Order of decreasing: CaS> LiCl> CsCl. That is CsCl has the lowest lattice energy.

Explanation:

LATTICE ENERGYcan be used to estimate the STRENGHT of the bonds in an ionic compound.

ATOMIC RADIUS is a function of lattice energy. The atomic radius INCREASES as you move DOWN a group. LATTICE ENERGY DECREASES as ATOMIC RADIUS increases.

Considering the cations Lithium +1, and Caesium +1 , as one move DOWN the GROUP the ions get larger, this causes the LATTICE ENERGY TO DECREASE DOWN THE GROUP. This means that between lithium in and caesium ion, the Caesium ion has LOWER LATTICE ENERGY as COMPARE TO LITHIUM ION.

AS ONE MOVE ACROSS THE PERIOD, POSITIVE IONS BECOMES MORE CHARGED, and the MORE THE CHARGE, THE GREATER THE LATTICE ENERGY.

Therefore, Calcium ion will have higher lattice energy than Lithium ion.

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3 years ago

Calculate the rate speed per drop in minute when applying a drip of 1000mg to last 4 2 hours

Mnenie [13.5K]

Answer:

42 hours is 2520 minutes...

If 1000 mg drops in 2520 minutes,

Then in 1 minute, (1000/2520) drop drops...

Which is approximately 0.40 drops.

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