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2017-03-22 16:13:50 UTC

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PermalinkHello,

I've attempted to solve the following problem, but I'm not sure of my

answer. If correct, can someone explain why - and if incorrect, can someone

explain where I made the error?

The thermal decomposition of 1.6608 g of MgSO4 * H2O produces 1.4446 g of a

1) MgSO4 * H2O(s) -> MgSO4(s) + H2O(g)

2) MgSO4 * H2O(s) -> MgO(s) + SO3(g) + H2O(g)

Complete the following table, and then identify the correct solid product by

comparing the calculated masses of MgSO4 and MgO with the observed mass of

the product.

Formula

Substance Weight Moles Mass (g)

-----------------------------------------------------

MgSO4 * H2O __________ __________ __________

MgSO4 __________ __________ __________

MgO __________ __________ __________

Because the observed mass of the product is 1.4446 g, the product is

__________.

**************************************

** HERE'S HOW I COMPLETED THE TABLE **

**************************************

Formula

Substance Weight Moles Mass (g)

-----------------------------------------------------

MgSO4 * H2O _138.4____ _0.0120___ _1.6608___

MgSO4 _120.4____ _0.0120___ _1.4446___

MgO __40.31___ _0.0358___ _1.4446___

******************

** HOW I DID IT **

******************

http://www.encyclopedia.com/articlesnew/17182.html

My lab manual (that the question comes from) is from a different company

than my text book and for whatever reason, I was unable to find the term

"Formula Weight" in the Glossary of my text book.

Next, I entered the known mass listed in the beginning of the problem. It

said "by comparing the calculated masses... with the observed mass of the

product".

Next I attempted to calculate the number of moles of each sample based on

the Formula Weight and the Mass of each substance. Here, I used a formula

Mass (g) x ( 1 mol / Atomic Mass ) = Number of moles

16.3 g S x ( 1 mol S / 32.07 g S ) = 0.508 mol S

Because the observed mass of the product is 1.4446 g, the product is

_MgSO4____.

I said this because I know that the answer is either MgSO4 or MgO. In the

Moles column of the talbe I completed, the values for MgSO4 * H2O and MgSO4

were very close while the value for MgO seemed larger.

It seems to me though that the values from the Moles column for MgSO4 and

MgO should be smaller than that for MgSO4 * H2O, especially after the H2O is

gone.

So, am I correct? Did I make some horrible assumption or error to come to

this conclusion?

My apologies if this is the incorrect place to post this type of question.

Of all of the newsgroups on my NNTP server, this seemed the most likely to

result in an intelligent and timely response (I'd like to know your opinions

before I head to class at 4:30 PM EDT).

Regards,

Neb Okla

What qualitative test could be used to substantiate this result? and What special safety precautions have been citied in this experiment?I've attempted to solve the following problem, but I'm not sure of my

answer. If correct, can someone explain why - and if incorrect, can someone

explain where I made the error?

The thermal decomposition of 1.6608 g of MgSO4 * H2O produces 1.4446 g of a

1) MgSO4 * H2O(s) -> MgSO4(s) + H2O(g)

2) MgSO4 * H2O(s) -> MgO(s) + SO3(g) + H2O(g)

Complete the following table, and then identify the correct solid product by

comparing the calculated masses of MgSO4 and MgO with the observed mass of

the product.

Formula

Substance Weight Moles Mass (g)

-----------------------------------------------------

MgSO4 * H2O __________ __________ __________

MgSO4 __________ __________ __________

MgO __________ __________ __________

Because the observed mass of the product is 1.4446 g, the product is

__________.

**************************************

** HERE'S HOW I COMPLETED THE TABLE **

**************************************

Formula

Substance Weight Moles Mass (g)

-----------------------------------------------------

MgSO4 * H2O _138.4____ _0.0120___ _1.6608___

MgSO4 _120.4____ _0.0120___ _1.4446___

MgO __40.31___ _0.0358___ _1.4446___

******************

** HOW I DID IT **

******************

http://www.encyclopedia.com/articlesnew/17182.html

My lab manual (that the question comes from) is from a different company

than my text book and for whatever reason, I was unable to find the term

"Formula Weight" in the Glossary of my text book.

Next, I entered the known mass listed in the beginning of the problem. It

said "by comparing the calculated masses... with the observed mass of the

product".

Next I attempted to calculate the number of moles of each sample based on

the Formula Weight and the Mass of each substance. Here, I used a formula

Mass (g) x ( 1 mol / Atomic Mass ) = Number of moles

16.3 g S x ( 1 mol S / 32.07 g S ) = 0.508 mol S

Because the observed mass of the product is 1.4446 g, the product is

_MgSO4____.

I said this because I know that the answer is either MgSO4 or MgO. In the

Moles column of the talbe I completed, the values for MgSO4 * H2O and MgSO4

were very close while the value for MgO seemed larger.

It seems to me though that the values from the Moles column for MgSO4 and

MgO should be smaller than that for MgSO4 * H2O, especially after the H2O is

gone.

So, am I correct? Did I make some horrible assumption or error to come to

this conclusion?

My apologies if this is the incorrect place to post this type of question.

Of all of the newsgroups on my NNTP server, this seemed the most likely to

result in an intelligent and timely response (I'd like to know your opinions

before I head to class at 4:30 PM EDT).

Regards,

Neb Okla