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3 years ago

Why do elements in the same group have similar chemical properties?

Chemistry

1 answer:

Sidana [21]3 years ago

4 0

Because their atoms have the same number of electron in the highest occupied level.

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Considering that the mantle is 44.8% oxygen and 21.5% silicon by mass, calculate the mole ratio of oxygen atoms to silicon atoms

horrorfan [7]

The mantle has a mass of around $4.278 X 10 ^2^4 kg$ that is around 68.4% of earth's mass.

So to calculate moles we need to first find out the mass of oxygen and silicon present in mantle. It is given that oxygen is 44.8% by mass in mantle and 21.5% by mass in mantle, therefore to calculate its mass, we need to use $\text{mass percentage }=\frac{\text{mole of solute}}{\text{mass of solution}}\times100$

Now, to calculate mass percentage of oxygen

$44.8 =\frac{x}{4.278X10^2^4kg}\times100$

$x= 191.65\times10^2^2kg$

Similarly the mass of silicon can be calculated

$21.5 =\frac{x}{4.278X10^2^4kg}\times100$

$x=91.977\times10^2^2kg$

Now, the moles of any substance is calculated by

$\text{moles}= \frac{\text{given mass}}{\text{molar mass}}$

$\text{moles of oxygen}= \frac{191.65\times10^2^2kg}{2.6566962\times10^-^2^6kg}$

where, mass of oxygen in kilograms is $2.6566962\times10^-^2^6kg$

So, $\text{moles of oxygen}=72.1384\times10^4^8\text{moles of O}$

Similarly $\text{moles of silicon}= \frac{91.977\times10^2^2kg}{4.663\times10^-^2^6kg}$

$\text{moles of silicon}=19.724\times10^4^8\text{moles of Si}$

Now, to calculate mole ratio we need to divide every moles to the lowest calculated mole that is the moles of Si and round it off to the nearest whole number.

$\text{mole ratio of oxygen}= \frac{72.138\times10^4^8kg}{19.724\times10^4^8kg}$

$=3.65\approx 4$

$\text{mole ratio of Silicon}=\frac{19.724\times10^4^8}{19.724\times10^4^8}$

$=1$

$\text{Mole ratio of Oxygen : Mole ratio of Silicon} = 4:1$

6 0

4 years ago

Read 2 more answers

Round 0.002346 to 3 significant figures.

Kruka [31]

Answer:

0.00235

Explanation:

Zeros that come before any non-zero digits are never significant.

Zeros that are in between any non-zero digits are always significant.

Zeros that come after any non-zero digit are ONLY significant if a decimal point in present somewhere in the number. (In this case there is a decimal point, but there aren't any zeros at the end of this number.)

The zeros at the beginning aren't significant, so include those zeros in your answer. The 6 at the end in greater than 5 so that rounds the 4 to up one number (In this case, it's 5).

This gives you 0.00235

6 0

3 years ago

Liquid does not act that a solid. how is it different from a solid and gas?

Wittaler [7]

Unlike solid matter, where particles are tightly packed and slightly vibrating, or gas, where particles go around everywhere and are extremely loose, a liquid has particles that are loosely packed but are still in slight contact with each other. Hope that's good enough

6 0

3 years ago

Don't know the answer

STatiana [176]

I believe that The answer is

3 0

4 years ago

Someone help please I don’t know the answer to the question I meeed help

mihalych1998 [28]

Answer: 143.3

137+115+104+263+98 divided by 5.Which gives us 143.3

5 0

3 years ago