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Convert the following into balanced equations:

(a) When gallium metal is heated in oxygen gas, it melts and forms solid gallium (III) oxide.

(b) Liquid hexane burns in oxygen gas to form carbon dioxide gas and water vapor.

(c) When solutions of calcium chloride and sodium phosphate are mixed, solid calcium phosphate forms and sodium chloride remains in solution.

a)

$4 \mathrm{Ga}(\mathrm{s})+3 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{Ga}_{2} \mathrm{O}_{3}(\mathrm{s})$

b)

$2 \mathrm{C}_{6} \mathrm{H}_{14}(\mathrm{l})+19 \mathrm{O}_{2}(\mathrm{g})-12 \mathrm{CO}_{2}(\mathrm{g})+14 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})$

c)

$3 \mathrm{CaCl}_{2}(\mathrm{aq})+2 \mathrm{Na}_{3} \mathrm{PO}_{4}(\mathrm{aq}) \longrightarrow \mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}(\mathrm{s})+6 \mathrm{NaCl}(\mathrm{aq})$

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University of Central Florida

University of Maryland - University College

Numerade Educator

Brown University

given a description of a chemical reaction, we can take this description and write it in a balanced chemical equation by first identifying the formulas for the substances involved and then balancing by changing the coefficients. So, for example, when gallium metal is heated, an oxygen gas it melts and form solid gallium oxide. So we know that we're starting off with gallium metal. Gallium is an element, and when I looked on the periodic table, the symbol for gallium his G uh, it's a metal, so that means it's a solid. It reacts with oxygen gas. Oxygen is a dye atomic element, and so exists as 02 and chemical reactions. It reacts to form the substance. Gallium three oxide gallium three is an ionic compound with a plus three charge. An oxide is the oxygen, and I end with the minus two charge. And so the formula for the neutral compound is G A to 03 So the product his g A to 03 which is a solid. So this is called our skeleton equation. Where we have the substance is written up the balance We changed the coefficients. I am one gallium on this side and two on this side have to oxygen's here and three accidents here. So I look for the lowest common multiple of the oxygen's, which means that I have to multiply this side by two on this side by three. So now I have six Oxygen's on both side, three times to and two times three. It's also changes the gallons on this that have two times two or four, which means I need to have four gallons here. So the balanced equation is for G A S plus 3 +02 g makes two g A 203 s. A second example has liquid heck sane burning an oxygen gas to form carbon dioxide gas and water vapor. You don't know what hexane is. It's a hydrocarbon, which means it has carbon and hydrogen. The heck sane is a six for carbon, and there are 14 hydrogen and this is a liquid. So we right l it reacts with oxygen, which again is oh to gas to form carbon dioxide, which is carbon with two oxygen's and water vapour. Water is H 20 and vapors. Another word for gas. These can be a little tricky to balance so we start with our carbons on this side. There are six, so put a six. Here there are 14 hydrogen is which would make me think a seven goes here seven times. Two. When I look at my oxygen's, I have 12 oxygen's plus seven or 19 oxygen's, which is an odd number. So over here I have a die atomic oxygen so I can put 19 have in order to get 19. But I can't leave it like that because that's not a whole number. So I then go through and multiply everything else by two to get rid of that. So this should be a two, 19 12 and 14. The last example looks at ionic compounds. I have solutions of calcium chloride and sodium phosphate, and they make a solid calcium phosphate as well as a solution of sodium chloride. So I have different ionic compounds that I need to find the formulas for. So calcium chloride is made up of the C A two plus ion and the C L minus. I on or see a seal, too. Sodium faucet is the n A plus. Ion and phosphate is the poly atomic ion P o for three minus or an A three p o for calcium phosphate is see a two plus combined with P O for three minus or C a three p 04 two and finally an A C L is in a plus and C l minus or in a c. L. So to write the balanced equation, they have see a feel too, which is in solution. So we write a que plus on a three p a for also a quist solution or a que make solid calcium class fate. So see a three p o for two, which is a solid. So in parentheses, s plus a quiz and a meal. And when we look to balance, we can see on this side we'll start with their calcium. Is there are three calcium someone for three here, which makes six chlorine six here and the two here to balance the sodium and classmates