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2 years ago

Please if you just want point TELL ME I can’t fail this.

Chemistry

1 answer:

Firlakuza [10]2 years ago

5 0

Answer:

here you go. I took the test :)

Explanation:

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If a substance has a half life of 58 years and starts with 500 g radioactive, how much remains radioactive after 30 years?

Vilka [71]

Answer:

A = 349 g.

Explanation:

Hello there!

In this case, since the radioactive decay kinetic model is based on the first-order kinetics whose integrated rate law is:

$A=Ao*exp(-kt)$

We can firstly calculate the rate constant given the half-life as shown below:

$k=\frac{ln(2)}{t_{1/2}} =\frac{ln(2)}{58year}=0.012year^{-1}$

Therefore, we can next plug in the rate constant, elapsed time and initial mass of the radioactive to obtain:

$A=500g*exp(-0.012year^{-1} *30year)\\\\A=349g$

Regards!

5 0

2 years ago

State the valency of Al in Al²03

kirill [66]

Answer:

jhy

Explanation:

uythi;ghto

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4 0

2 years ago

How many moles of nitrogen, N, are in 61.0 g of nitrous oxide, N2O?

Oksana_A [137]

Answer:

2.77 mol N

Explanation:

M(N2O) = 2*14 + 16 = 44 g/mol

61.0 g * 1 mol/44g = (61/44) mol N2O

N2O ---- 2N

1 mol 2 mol

(61/44) mol x mol

x = (61/44)*2/1 = 2.77 mol N

4 0

2 years ago

The balanced redox reactions for the sequential reduction of vanadium are given below.

Minchanka [31]

Answer : 0.0392 grams of Zn metal would be required to completely reduced the vanadium.

Explanation :

Let us rewrite the given equations again.

$2VO_{2}^{+} (aq)+ 4H^{+}(aq) + Zn (s)\rightarrow 2VO^{2+}(aq)+Zn^{2+}+2H2O(l)$ $2VO^{2+}(aq)+ 4H^{+}(aq) + Zn (s)\rightarrow 2V^{3+} (aq)+Zn^{2+}+2H2O(l)$

$2V^{3+} (aq)+ Zn (s)\rightarrow 2V^{2+}(aq)+Zn^{2+}(aq)$

On adding above equations, we get the following combined equation.

$2VO_{2}^{+} (aq)+ 8H^{+} (aq) + 3Zn (s)\rightarrow 2V^{2+}(aq)+3Zn^{2+}(aq)+4H_{2}O(l)$

We have 12.1 mL of 0.033 M solution of VO₂⁺.

Let us find the moles of VO₂⁺ from this information.

$12.1 mL \times \frac{1L}{1000mL}\times \frac{0.033mol}{L}=0.0003993mol NO_{2}^{+}$

From the combined equation, we can see that the mole ratio of VO₂⁺ to Zn is 2:3.

Let us use this as a conversion factor to find the moles of Zn.

$0.0003993mol NO_{2}^{+}\times \frac{3mol Zn}{2molNO_{2}^{+}}=0.00059895mol Zn$

Let us convert the moles of Zn to grams of Zn using molar mass of Zn.

Molar mass of Zn is 65.38 g/mol.

$0.00059895mol Zn\times \frac{65.38gZn}{1molZn}=0.0392gZn$

We need 0.0392 grams of Zn metal to completely reduce vanadium.

6 0

2 years ago

What is the volume of an object with a density of 24.5 g/cm³ and a mass of 8.2 g?

vitfil [10]

<u>Answer:</u> The correct answer is option A.

<u>Explanation:</u>

To calculate the volume of an object, we use the formula:

$Density=\frac{\text{Mass of an object}}{\text{Volume of an object}}$

We are given:

Density of an object = $24.5g/cm^3$

Mass of an object = 8.2 grams

Volume of an object = ?

Putting values in above equation, we get:

$24.5g/cm^3=\frac{8.2g}{Volume}$

$Volume=0.33cm^3$

Hence, the correct answer is Option A.

6 0

2 years ago