Science Tutor: Chemistry Name: Mixtures, Solutions, &Compounds;: Chemical Equati

Question

Science Tutor: Chemistry Name: Mixtures, Solutions, &Compounds;: Chemical Equations Date Chemical Equations If a chemical symbol can be thought of as a letter and a chemical formula as a word in the language of chemistry, then a chemical equation is a statement or sentence. A chemical equation is a shorthand way of describing a chemical reaction between two or more substances. A "+ sign means "combines with." An arrow points away from the reactants and toward the products (See page 10), and an arrow means "yields." 2Na + Cl2 2NaCl means sodium combines with chlorine to yield sodiumn chloride (salt) Look closely at the equation above. Notice the "2" in front of NaCI on the right and Na on the left. That 2, called a coefficient, is necessary to make this equation balance. Remember Antoine Lavoisier? (Page 15) Matter is neither created nor destroyed in a chemical reaction. The same number of each kind of atom must be on both sides of a chemical equation. Because chlorine only exists as a molecule consisting of two chlorine atoms, it requires two atoms of sodium to yield two molecules of salt (NaCI). This illustrates another important law stated clearly by the French chemist Joseph-Louis Proust in 1799. Chemical compounds always combine in certain specific fixed proportions. Wherever sodium and chlorine combine, two atoms of sodium will be necessary to react with one molecule of gaseous chlorine. 1 . For the equation 2Mg + O2 2MgO + energy: A. List the reactant or reactants 2Hato B. List the product or products C. How many atoms of magnesium does it take to combine with one molecule of oxygen? D. How many molecules of magnesium oxide are produced in this reaction? 2. Hydrogen can combine with oxygen to produce water. We could write the equation like this: H2 + O2 H2O. But this equation is unbalanced! Rewrite this equation with the correct coefficients so that an atom of oxygen doesn't disappear! (Be careful. If you add a coefficient to one side you may have to adjust the other. Count all the atoms.) 3. Now that you have the idea, balance the following equations: A, Pho, PbO + 02 C. Ca + H2O Ca(OH)2 + H2 How is following a recipe to mix up a batch of biscuits (or any other food item) similar to Proust's law for chemical reactions? 4. OMark Twain Media, Inc., Publishers 17

Explanation / Answer

Q1-C

From the reaction it can be seen that 2 atoms of Mg and 1 Molecule of O2 combine to form 2 molecules of MgO

Q1-D

2 molecules of Mg are produced according to the balanced reaction,

Q2

The balanced equation in which all the components of products and reactants are same is:

2H2+O2 -> 2H2O

Here we can see all the atoms are balanced as there are 4 atoms on both sides and 2 O atom on both sides

Q3

Similarly balancing atoms on both sides we get the following balanced equations.

Q4

As we get biscuits only after mixing the ingredients in right proportions similar is the case for chemical reactions as when we will mix the reactants in the right proportions only then we will get the right product.

Please do give a thumbs up as it matters a lot and leave a comment in case there are doubts.

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