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[Waki]

Bump- does anyone know simple trigonometry? I'd like to get some knowledge on the topic❤️

[aequilibrium]

@Waki - What exactly would you like to know? I can help you a little bit ^-^
If you want something a little detailed I'm afraid I won't be able to answer you today since I'm a little busy, sorry... But I can totally help you with anything tomorrow if no one else is available c:

[ryunosuke akutagawa]

TYPE OF QUESTION:
Math
YOUR QUESTION:

There were some 20¢ and 50¢-coins in a box. The number of 20¢-coins is 1/4 the number of 50¢-coins. John exchanged 18 50¢-coins for the same amount of money in 20¢-coins. The ratio of the new number of 20¢ coins to the new number of 50¢ coins is 10:7. How much money is there in the box?
(the answer is $33, but i used guess and check for that answer, and there's definitely a better way.)

[Waki]

Up

[Mewfle]

-

[aequilibrium]

@ryunosuke akutagawa


x will be the number of 20¢ coins and y the number of 50¢ coins.

So, initially, x = 1/4 y. If he exchanged 18 50s, the number of 50¢ coins will now be y - 18

To know how many 20¢ coins he received, you have:

50 x 18 = 900¢
900 / 20 = 45 20¢ coins

x + 45 is the new number of 20¢ coins. So now, if the 20 to 50 ratio is 10:7, it means that if you divide the amount of 20¢ coins by the number of 50¢ coins this is the fraction you will get. So you can use a system to determine the exact number of each coins.

( x + 45 ) / ( y - 18 ) = 10 / 7
x = 1/4 y

( 1/4 y + 45 ) / ( y - 18 ) = 10 / 7
-

1/4 y + 45 = 10/7 y - 180/7
-

33/28 y = 495/7
-

y = 60
x = 1/4 x 60

y = 60
x = 15

total value = 15 x 20 + 60 x 50 = 3300¢ = 33$




@Mewfle - Could you give us an example of when that happens? I don't remember a lot from chemistry now, but I might remember something and help you out if you give me a specific example ^-^

[CᴀɴᴅʏNᴜᴛᴍᴇɢ]

I HAVE A QUESTION!
TYPE OF QUESTION:
Science
YOUR QUESTION:
Alright, I don't get cations and anions? Like, after they combine to make a ionic compound, why is there sometimes a number but then sometimes there isn't? I get that they cancel each other out and such, but then why do they only sometimes have a few left over? (Sorry...not very good at explaining >.<)

First thing to remember: cations lose electrons (metals, positive charge), anions gain electrons (non-metals; negative charge).

All ionic compounds you study will have a net charge of 0 (= they balance each other's positive/negative charges out). This happens in a certain way, where, let's say you have oxygen and hydrogen bonding to form water (easy example to think of). Hydrogen and oxygen both only have one charge - every atom of hydrogen loses an electron, and every atom of oxygen gains two electrons. However, if you only had one hydrogen and one oxygen, you'd have a net charge of 1- instead of 0. To solve this problem, you take an extra hydrogen. Now, the two 1- charges from the two hydrogens balance out the one 2+ charge from the oxygen.

To indicate that you have a certain amount of atoms of Element X, you write the element symbol - X, and then the number of atoms of it in subscript - X2 would be two atoms of Element X, for example. In our earlier example, you would call the compound with two hydrogen atoms and one oxygen atom H2O. You don't need to indicate the number of oxygen atoms, because if there's no number, you always assume there's one atom, and we do only have one oxygen atom present.
This is the basic compound-forming convention.

If you have a multivalent element, which has two charges...
Elements in the middle of the periodic table (can) have two charges - iron, for example, can be 2+ or 3+.
Follow the same steps, but make sure you're balancing the correct charge. For example, iron can bond with oxygen (forms iron oxide = rust), in two ways. It could be iron's 2+ charge and oxygen's 2- charge bonding in a 1:1 ratio, forming FeO, or iron's 3+ charge bonding with oxygen's 2- charge in a 2:3 ratio, forming Fe2O3.

One easy way to remember how many atoms of each element you need is the criss-cross method. So, if you have iron 3+ and oxygen 2-, take the number of each charge, ignore the positive/negative sign and that's the number of atoms of the other element required. 3+ charge on iron = 3 oxygen atoms necessary. 2- charge on oxygen = 2 iron atoms required.

I'm not sure whether you've learned this, by the way, but there are two types of chemical compound formulas; molecular and empirical. I've always been told to use empirical - it's simpler, but your class may vary.
Let's go back to the FeO example. I called this compound FeO because this is its empirical formula, and it cannot be simplified further. However, the compound's formula is technically Fe2O2 - this is its molecular formula. You can see that both the subscripts are divisible by 2 to get a whole number (1). Therefore, you can simplify its molecular formula down to the empirical. Sometimes, the molecular formula is the same as the empirical, if you cannot simplify it while maintaining whole-number subscripts - Fe2O3, for example.

Ehh, enjoy your handy chem reference guide, I'm sorry for writing you an essay [pfft no I'm not]. <3
Feel free to PM me if you have any more questions, I love this complicated stuff. c:

[Eagle's Eye]

--
nevermind answered^^

[Waki]

up

[Waki]

I HAVE A QUESTION!
TYPE OF QUESTION:
Science
YOUR QUESTION:
Alright, I don't get cations and anions? Like, after they combine to make a ionic compound, why is there sometimes a number but then sometimes there isn't? I get that they cancel each other out and such, but then why do they only sometimes have a few left over? (Sorry...not very good at explaining >.<)

First thing to remember: cations lose electrons (metals, positive charge), anions gain electrons (non-metals; negative charge).

All ionic compounds you study will have a net charge of 0 (= they balance each other's positive/negative charges out). This happens in a certain way, where, let's say you have oxygen and hydrogen bonding to form water (easy example to think of). Hydrogen and oxygen both only have one charge - every atom of hydrogen loses an electron, and every atom of oxygen gains two electrons. However, if you only had one hydrogen and one oxygen, you'd have a net charge of 1- instead of 0. To solve this problem, you take an extra hydrogen. Now, the two 1- charges from the two hydrogens balance out the one 2+ charge from the oxygen.

To indicate that you have a certain amount of atoms of Element X, you write the element symbol - X, and then the number of atoms of it in subscript - X2 would be two atoms of Element X, for example. In our earlier example, you would call the compound with two hydrogen atoms and one oxygen atom H2O. You don't need to indicate the number of oxygen atoms, because if there's no number, you always assume there's one atom, and we do only have one oxygen atom present.
This is the basic compound-forming convention.

If you have a multivalent element, which has two charges...
Elements in the middle of the periodic table (can) have two charges - iron, for example, can be 2+ or 3+.
Follow the same steps, but make sure you're balancing the correct charge. For example, iron can bond with oxygen (forms iron oxide = rust), in two ways. It could be iron's 2+ charge and oxygen's 2- charge bonding in a 1:1 ratio, forming FeO, or iron's 3+ charge bonding with oxygen's 2- charge in a 2:3 ratio, forming Fe2O3.

One easy way to remember how many atoms of each element you need is the criss-cross method. So, if you have iron 3+ and oxygen 2-, take the number of each charge, ignore the positive/negative sign and that's the number of atoms of the other element required. 3+ charge on iron = 3 oxygen atoms necessary. 2- charge on oxygen = 2 iron atoms required.

I'm not sure whether you've learned this, by the way, but there are two types of chemical compound formulas; molecular and empirical. I've always been told to use empirical - it's simpler, but your class may vary.
Let's go back to the FeO example. I called this compound FeO because this is its empirical formula, and it cannot be simplified further. However, the compound's formula is technically Fe2O2 - this is its molecular formula. You can see that both the subscripts are divisible by 2 to get a whole number (1). Therefore, you can simplify its molecular formula down to the empirical. Sometimes, the molecular formula is the same as the empirical, if you cannot simplify it while maintaining whole-number subscripts - Fe2O3, for example.

Ehh, enjoy your handy chem reference guide, I'm sorry for writing you an essay [pfft no I'm not]. <3
Feel free to PM me if you have any more questions, I love this complicated stuff. c:

just like they said, Cations lose electrons (positive) while Anions gain (negative)

A good way to remember this is: a PAWsitive ion is called a CATion, and a negative ion is called an Anion.
It is easy to remember because you can relate PAWsitive to CAT (as cats have paws)

The numbers beside each element indicate the charge it would have as an ion. The numbers are how many electrons are needed or lost to give the element a FULL valence shell. For example, Sodium (Na) has a charger of +1, meaning that it would need to LOSE an electron to have a full valence shell and to become an ion (it needs to lose because Cations lose electrons. A good way to remember this (+ means take away and - means add) Is the saying " When you remove negative things from your life it becomes positive", so +1 would be removing one electron from the valence)

Going back to the Sodium example, Sodium is number 11 on the periodic table
the atomic number is 11, so sodium would have 11 electrons in total.
(2, 8, 1)
Sodium is very unstable (As an Alkali metal, it does not have a full valence shell making it very reactive with certain elements)
Making sodium an Ion would be taking away 1 electron from the valence shell (+1)
and it would become a CATION as it would have a PAWsitive charge

When it becomes a cation, you draw the 8 valence electrons in your Lewis dot/Bohr diagram, put brackets around the diagram and outside of the diagram on the top right corner put the charge of +1 as the element needed to remove one electron in order to become stabilized.

^^what was explained above was ions (Cations and Anions)
however Ionic compounds are different, remember that Ionic compounds are only between a metal and a non metal (positive and negative charges attract only), and they transfer electrons to each other to make both valence shells full.

For example, NaCl is the most common Ionic compound (table salt)
Sodium having 11 electrons (2.8,1)
and Chlorine having 17 (2,8,7)

They both do not have full valence shells (the electrons on the most outer shell)
To require a full shell,
- Chlorine would need 1 electron.
-Because Sodium has an extra electron, Sodium and Chlorine would join together to form a IONIC COMPOUND,
-in which Sodium gives one electron to Chlorine (Na)+1 and chlorine taking that 1 electron (Cl)-1
-(remember +1 means taking AWAY an electron and -1 means RECEIVING )
-and because they have joined together, BOTH of the elements now have full valence shells,
-sodium with 8 electrons on the valence, and Chlorine with 8.
-It is now a stable pure substance and does not react with water like pure sodium would.

hope this helped