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insens350 [35]
4 years ago
13

An organism had 1,000 grams of carbon-14 (a radioactive form of carbon) in it when it died. How much remains after five half-liv

es?
Chemistry
1 answer:
Katarina [22]4 years ago
5 0

Answer:

After 5th half life the remaining mass is 31.25 g.

Explanation:

Given data:

Total mass of carbon-14 = 1000 g

Mass remain after 5 half lives = ?

Solution:

At time zero = 1000 g

At first half life = 1000 g/2 = 500 g

At second half life =  500 g/ 2= 250 g

At third half life = 250 g/ 2 = 125 g

At 4th half life = 125 g/2 = 62.5 g

At 5th half life = 62.5 g/2 = 31.25 g

Thus after 5th half life the remaining mass is 31.25 g.

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The density of acetonitrile (CH3CN) is 0.786 g/mL, and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by diss
ololo11 [35]

Answer:

The answer to your question is  0.22

Explanation:

Data

Acetonitrile (CH₃CN) density = 0.786 g/ml

Methanol (CH₃OH) density = 0.791 g/ml

Volume of CH₃OH = 22 ml

Volume of CH₃CN = 98.4 ml

Process

1.- Calculate the mass of Acetonitrile and the mass of Methanol

density = mass/ volume

mass = density x volume

Acetonitrile

        mass = 0.786 x 98.4

                  = 77.34 g

Methanol

        mass = 0.791 x 22

                  = 17.40 g

2.- Calculate the moles of the reactants

Acetonitrile molar mass = (12 x 2) + (14 x 1) + (3 x 1)

                                        = 24 + 14 + 3

                                        = 41 g

Methanol molar mass = (12 x 1) + (4 x 1) + (16 x 1)

                                      = 12 + 4 + 16

                                      = 32 g

Moles of Acetonitrile

                     41 g ----------------- 1 mol

                      77.34g ------------  x

                      x = (77.34 x 1) / 41

                      x = 1.89 moles

Moles of Methanol

                      32 g -------------- 1 mol

                       17.40 g ---------  x

                       x = (17.40 x 1)/32

                       x = 0.54 moles

3.- Calculate the mole fraction of Methanol

Total number of moles = 1.89 + 0.54

                                       = 2.43

Mole fraction = moles of Methanol / total number of moles

Mole fraction = 0.54/ 2.43

Mole fraction = 0.22  

6 0
4 years ago
What is the theoretical yield of vanadium, in moles, that can be produced by the reaction of 1.0 mole of V2O5 with 4.0 moles of
IRINA_888 [86]

Answer:

Theoretical yield of vanadium = 1.6 moles

Explanation:

Moles of V_2O_5 = 1.0 moles

Moles of Ca = 4.0 moles

According to the given reaction:-

V_2O_5_{(s)} + 5Ca_{(l)}\rightarrow 2V_{(l)} + 5CaO_{(s)}

1 mole of V_2O_5 react with 5 moles of Ca

Moles of Ca available = 4.0 moles

Limiting reagent is the one which is present in small amount. Thus, Ca is limiting reagent. (4.0 < 5)

The formation of the product is governed by the limiting reagent. So,

5 moles of Ca on reaction forms 2 moles of V

1 mole of Ca on reaction for 2/5 mole of V

4.0 mole of Ca on reaction for \frac{2}{5}\times 4 mole of V

Moles of V = 1.6 moles

<u>Theoretical yield of vanadium = 1.6 moles</u>

4 0
3 years ago
Which of these relationships is true of an uncharged atom?
marusya05 [52]

Answer:

The correct option is  C) The number of protons is equal to the number of electrons.

Explanation:

Atoms are made up of particles called protons, neutrons, and electrons. Protons and neutrons are in the center of the atom and form the nucleus, while electrons surround the nucleus. Electrons have a negative charge. The charge of the protons is positive and finally, the neutrons have no charge.

If the atom has no charge, this means that the total charge of the atomic nucleus, which is positive due to the presence of the protons, is equal to the negative charge of the electrons, so that it cancels out.

So, <u><em>the correct option is  C) The number of protons is equal to the number of electrons.</em></u>

7 0
3 years ago
What is the number of molecules present in 1.12 dm^3 of nitrogen gas at STP​
Anuta_ua [19.1K]

Answer:

\huge\boxed{\sf No.\ of\ molecules = 3 * 10\²\² \ molecules}

Explanation:

<u>Given Data:</u>

Volume = v = 1.12 dm³ = 1.12 L

Density of nitrogen at STP = D = 1.25 g / L

Molar mass = M = 14 * 2 = 28 g / mol

Avogadro's Number = \tt{N_{A}} = 6.023 * 10²³ mol⁻¹

<u>Required:</u>

No. of molecules = ?

<u>Formula:</u>

\tt{No. \ of \ molecules = \frac{Density * Volume}{Molar\ Mass} * N_{A}}

<u>Solution:</u>

No. of molecules = (1.25*1.12) / 28 * (6.023 * 10²³)

No. of molecules = ( 1.4 / 28 ) * 6.023 * 10²³

No. of molecules = 0.05 * 6.023 * 10²³

No. of molecules = 0.3 * 10²³

No. of molecules = 3 * 10²² molecules

\rule[225]{225}{2}

Hope this helped!

<h3>~AH1807</h3>
4 0
3 years ago
What holds the ions together in galena?
Monica [59]
It might be  electromagnetic force
4 0
3 years ago
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