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3 years ago

What is the mass,in grams,of 1.20x10^25 atoms of calcium?

Chemistry

2 answers:

kow [346]3 years ago

8 0

The mass of 1.20x10^25 atoms of Ca is 8000 grams

mariarad [96]3 years ago

7 0

Answer:

The mass of calcium in the given number of atoms is 797.2 g.

Explanation:

$N=n\times N_A$

N = Number of atoms/molecules

n = Moles of compound

$N_A$ = Avogadro number = $6.022\times 10^{23} mol^{-1}$

We have:

Number calcium atoms = $N=1.20\times 10^{25}$

n = moles of calcium = ?

$n=\frac{N}{N_A}=\frac{1.20\times 10^{25}}{6.022\times 10^{23} mol^{-1}}$

n = 19.93 mol

Atomic mass of calcium = 40 g/mol

Mass of 19.93 moles of calcium = 40 g/mol × 19.93 mol=797.2 g

The mass of calcium in the given number of atoms is 797.2 g.

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How many half-lives are required for the concentration of reactant to decrease to 1.56% of its original value?4247.56.56

neonofarm [45]

Answer:

6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.

Explanation:

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

Given:

Concentration is decreased to 1.56 % which means that 0.0156 of $[A_0]$ is decomposed. So,

$\frac {[A_t]}{[A_0]}$ = 0.0156

Thus,

$\frac {[A_t]}{[A_0]}=e^{-k\times t}$

$0.0156=e^{-k\times t}$

kt = 4.1604

The expression for the half life is:-

Half life = 15.0 hours

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

Where, k is rate constant

So,

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

$\frac{4.1604}{t}=\frac {ln\ 2}{t_{1/2}}$

$t = 6\times t_{1/2}$

<u>6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.</u>

6 0

3 years ago

The balanced equation for photosynthesis is shown below.

klio [65]

The true answer is: It's conserved because the total number of H atoms on each side is 12.
the first two answer is wrong because it's conserved not as mentioned, It's not conserved.

and the last one also wrong because the total number of O atoms are equal at the two sides but not equal 2.

3 0

3 years ago

Read 2 more answers

How do you balance a chemical equation

Dominik [7]

There should be mass balance and the charge balance between the reactants and the products

Mass balance : total no of individual atoms of each type should be balanced before and after the reaction

Charge balance : Overall charge of the reactants should be balanced with the overall charge of the products

You can balance,

1)by just looking at it

2)by Algebraic method given above or

3)by the redox method

You need to know how to get the oxidation numbers in order to use the oxidation method

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3 years ago

Ionic compounds involve a (share, tranfer) of electrons and typically involve atoms that have (Large, similar, very different) e

Juliette [100K]

Answer:

2 Transfer; very different

Explanation:

Ionic compound are compound that are formed from transfer of electron. The cations donate the electron(s) while the anion receive the electron(s). The compound possess a positively charged end and a negatively charge end. Example of ionic compound is NaCl . The sodium donates one electron to the chlorine to fulfill the octet rule. The sodium atom becomes positively charged as it donate electron to the chlorine atom. The chlorine atom becomes negatively charged as it receive electron from Sodium atom.

The atoms that are involve in forming ionic compound have very different electronegativity . Electronegativity is the measure of the ability of an atom to attract a bond pair of electron. For example the NaCl compound, the two atom has verse differences in the electronegativity. Cl atom is far more electronegative than Sodium atom.

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3 years ago

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PolarNik [594]

Answer:

They are multilayered

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Explanation:

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