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3 years ago

which part of earths interior is inferred to have convection currents that causes tectonic plates to move

1 answer:

5 0

Asthenosphere is inferred to have convection currents that cause tectonic plates to move because the material in this part of the mantle flows and can move plastically and convection is all about the movement of the magma,the hotter stuff rising towards the crust while the cooler stuff sinks deeper into the mantle.

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A certain element exists as two different isotopes. 90.50% of its atoms have a mass of 20.00 amu and 9.500% of its atoms have a

Serga [27]

Answer:

20.19 amu.

Explanation:

From the question given above, the following data were obtained:

Isotope A:

Abundance (A%) = 90.5%

Mass of A = 20 amu

Isotope B:

Abundance (B%) = 9.5%

Mass of B = 22 amu

Average atomic mass =..?

The average atomic mass of the element can be obtained as follow:

Average atomic mass = [(Mass of A × A%)/100] + [(Mass of B × B%)/100]

Average atomic mass = [(20 × 90.5)/100] + [(22 × 9.5)/100]

Average atomic mass = 18.1 + 2.09

Average atomic mass = 20.19 amu

Therefore, the average atomic mass of the element is 20.19 amu

6 0

3 years ago

How many days have passed if 4.80 mg of calcium-47 decayed to 1.2 mg of calcium-47?

LenaWriter [7]

(1) 36 days is 8 half-life periods,
so 24mg becomes 24mg times (1/2)^8 = 24 mg/256 = 0.094 mg

(2) 9.6/1.2 = 8, which means three half-life periods went by.
At the end of 4.5 days, there were 4.8 mg
At the end of 9.0 days, there were 2.4 mg
At the end of 13.5 days, there were 1.2 mg

(3) The activity is proportional to the amount of radioactive material remaining,
so after two half-life periods, the activity should be 1/4 of what it originally was.
So the initial activity was probably 12.0 Ci

6 0

3 years ago

1. Suppose 0.7542 g of magnesium reacts with excess oxygen to form magnesium oxide as the only product, what would be the theore

Alina [70]

Answer :

(1) The theoretical yield of product, $MgO$ is, 1.257 grams.

(2) The percent yield of $MgO$ is, 64.13 %

(3) If the percent yield is calculated to be over 100% then there might be some impurity present in the desired product.

Solution : Given,

Mass of Mg = 0.7542 g

Molar mass of Mg = 24 g/mole

Molar mass of MgO = 40 g/mole

First we have to calculate the moles of Mg.

$\text{ Moles of }Mg=\frac{\text{ Mass of }Mg}{\text{ Molar mass of }Mg}=\frac{0.7542g}{24g/mole}=0.03142moles$

Now we have to calculate the moles of $MgO$

The balanced chemical reaction is,

$2Mg(s)+O_2(g)\rightarrow 2MgO(s)$

From the reaction, we conclude that

As, 2 mole of $Mg$ react to give 2 mole of $MgO$

So, 0.03142 moles of $Mg$ react to give 0.03142 moles of $MgO$

Now we have to calculate the mass of $MgO$

$\text{ Mass of }MgO=\text{ Moles of }MgO\times \text{ Molar mass of }MgO$

$\text{ Mass of }MgO=(0.03142moles)\times (40g/mole)=1.257g$

Theoretical yield of $MgO$ = 1.257 g

Experimental yield of $MgO$ = 0.8922 g

Now we have to calculate the percent yield of $MgO$

$\% \text{ yield of }MgO=\frac{\text{ Experimental yield of }MgO}{\text{ Theretical yield of }MgO}\times 100$

$\% \text{ yield of }MgO=\frac{0.8922g}{1.257g}\times 100=70.97\%$

Therefore, the percent yield of $MgO$ is, 70.97 %

If the percent yield is calculated to be over 100% then the product would be greater than 1.257 g which indicates that there might be some impurity present in the desired product.

4 0

3 years ago

A chemist measures the amount of iodine solid produced during an experiment. she finds that 1.6 g of iodine solid is produced. c

Yakvenalex [24]

Mass of iodine solid produced = 1.6 g

Iodine solid has a molecular formula : I2

Atomic mass of iodine = 126.904 g/mol

Therefore, molar mass of I2 solid = 2* 126.904 = 253.808 g/mol

Number of moles of a given substance is the ratio of its mass to the molar mass

# moles of I2 solid = mass of I2 solid/molar mass = 1.6 g/253.808 = 0.00630 moles

Hence, the # moles of iodine solid produced is 0.00630 moles

3 0

3 years ago

What is the formula for aluminum oxide

Romashka [77]

The formula is AI203

4 0

3 years ago

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