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3 years ago

12

Explain why the melting point of calcium is high?

2 answers:

DanielleElmas [232]3 years ago

5 0

It takes more energy to breakdown the bonds

Assoli18 [71]3 years ago

3 0

Calcium has a high melting point which is about 842°C.

This is coz Calcium atoms have smaller radii since they have also a greater nuclear charge.

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How are stars and comets different?

ehidna [41]

The answer is letter C.

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3 years ago

Examine the diagram of a cell.

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Answer:

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What is the definition of quanititative observation

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3 years ago

In solid NaCl, the equilibrium separation between neighboring Na+ and Cl- ions is 0.283 nm. Calculate the coulombic energy betwe

const2013 [10]

Explanation:

It is given that r = 0.283 nm. As 1 nm = $10^{-9} m$ .

Hence, 0.283 nm = $0.283 \times 10^{-9} m$

Formula for coulombic energy is as follows.

$U_{coulomb} = -1.748 \frac{e^{2}}{4 \pi \epsilon_{o} r}$

where, e = $1.6 \times 10^{-19}$ C

$\epsilon_{o}$ = $8.85 \times 10^{-12}$

$U_{coulomb} = -1.748 \frac{(1.6 \times 10^{-19}^{2}}{4 \times 3.14 \times 8.85 \times 10^{-12} \times 0.283 \times 10^{-9}}$

= $1.423 \times 10^{-18} J$

As 1 eV = $1.6 \times 10^{-19} J$

So, 1 J = $\frac{1 eV}{1.6 \times 10^{-19}}$

Hence, U = $\frac{1.423 \times 10^{-18} J}{1.6 \times 10^{-19} J}$

= 8.9 eV

Also, 1 J = $\frac{10^{-3} kJ}{6.022 \times 10^{23}mol}$

= $1.67 \times 10^{-27}$ kJ/mol

Therefore, U = $1.423 \times 10^{-18} J \times 1.67 \times 10^{-27}$ kJ/mol

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3 years ago

at 55 years what mass remains of a 200.0 g sample of a radioactive isotope with a half life of 10.0 years

Harman [31]

Answer:

4.419 g

Explanation:

55 years is 5.5 half lives

200 g * (1/2)^5.5 = 4.419 g

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1 year ago