Which of these is a chemical property of a substance?

If 12.5 grams of the original sample of cesium-137 remained after 90.6 years, what was the mass of the original sample?

myrzilka [38]

Answer:

Mass of original sample = 100 g

Explanation:

Half life of cesium-137 = 30.17 years

$t_{1/2}=\frac {ln\ 2}{k}$

Where, k is rate constant

So,

$k=\frac{\ln2}{t_{1/2}}$

$k=\frac{\ln2}{30.17}\ year^{-1}$

The rate constant, k = 0.02297 year⁻¹

Time = 90.6 years

Using integrated rate law for first order kinetics as:

$[A_t]=[A_0]e^{-kt}$

Where,

$[A_t]$ is the concentration at time t

$[A_0]$ is the initial concentration

Initial concentration $[A_0]$ = ?

Final concentration $[A_t]$ = 12.5 grams

Applying in the above equation, we get that:-

$12.5\ g=[A_0]e^{-0.02297\times 90.6}$

$[A_0]=\frac{12.5}{e^{-0.02297\times 90.6}}\ g=100\ g$

Mass of original sample = 100 g

8 0

3 years ago

In a very violent reaction called a thermite reaction, aluminum metal reacts with iron (III) oxide to form iron metal and alumin

leva [86]

Here's the equation:
Fe2 O3 + 2Al → 2Fe + Al2 O3

Here's the question.
What mass of Al will react with 150g of Fe2 O3?

In every 2 moles Al you need 1 mole Fe2O3 

moles = mass / molar mass 
moles Fe2O3 = 150 g / 159.69 g/mol 
= 0.9393 moles 

moles Al needed = 2 x moles Fe2O3 
= 2 x 0.9393 mol 
= 1.879 moles Al needed 

mass = molar mass x moles 
mass Al = 26.98 g/mol x 1.879 mol 
= 50.69 g 
= 51 g (2 sig figs)

So the mass of Al that will react with 150g of Fe2 O3 is 51 grams.

3 0

3 years ago

Iron (III) oxide reacts with solid carbon in the followed reaction: 2Fe2O3(s) + 3C(s) → 4Fe(s) + 3CO2(g) What mass of Fe2O3 is n

Veseljchak [2.6K]

953.6 g of iron (III) oxide (Fe₂O₃)

Explanation:

We have the following chemical reaction:

2 Fe₂O₃ (s) + 3 C (s) → 4 Fe (s) + 3 CO₂ (g)

We calculate the number of moles of CO₂ by using the following formula:

pressure × volume = number of moles × gas constant × temperature

number of moles = (pressure × volume) / (gas constant × temperature)

number of moles of CO₂ = (2.1 × 100) / (0.082 × 300)

number of moles of CO₂ = 8.54 moles

Taking in account the chemical reaction we devise the following reasoning:

if 2 mole of Fe₂O₃ produces 3 mole of CO₂

then X moles of Fe₂O₃ produces 8.54 mole of CO₂

X = (2 × 8.54) / 3 = 5.69 moles of Fe₂O₃

number of moles = mass / molar weight

mass = number of moles × molar weight

mass of Fe₂O₃ = 5.69 × 160 = 953.6 g

Learn more about:

number of moles

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6 0

2 years ago

Read 2 more answers

Which laws can be combined to form the ideal gas law? Boyle’s law and Charles’s law Gay-Lussac’s law and Avogadro’s law Charles’

kolezko [41]

Ideal gas law is a combination of three gas laws, which are Boyle's law, Charles' law and Avogadro's law. Ideal gas law states that PV = nRT, where:
P = pressure of the gas
V = volume of the gas
n = no of moles of the gas
R = universal gas constant
T = absolute temperature in Kelvin

7 0

3 years ago

Read 2 more answers

If 15.00 mL of 0.0100 M Ca(IO3)2 solution are mixed with 0.500 g KI, what is the theoretical yield (in grams) of I2?

n200080 [17]

The theoretical yield of I2 in the reaction would be 0.23 g

<h3>Theoretical yield</h3>

This refers to the stoichiometric yield of a reaction.

From the equation of the reaction:

Ca(IO3)2 + 10 KI + 12 HCl → 6 I2 + CaCl2 + 10 KCl + 6 H2O

The mole ratio of Ca(IO3)2 and I2 is 1: 6

Mole of 15.00 mL, 0.0100 M Ca(IO3)2 = 15/1000 x 0.0100

= 0.00015 mole

Equivalent mole of I2 = 0.00015 x 6

= 0.009 mole

mass of 0.0009 I2 = 0.0009 x 253.809

= 0.23 g

More on stoichiometric calculations can be found here: brainly.com/question/6907332

8 0

2 years ago