CHE 1110 Lecture Notes - Lecture 4: Stoichiometry, Ionic Compound, Significant Figures

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ultramarinesheep300

18 Sep 2018

School

St. John's University

Department

Chemistry

Course

CHE 1110

Professor

Jack Preses

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How much of this reacts with how much of that to make how much of the other thing. The si unit for the amount of substance is the mole. A mole is defined as the number of atoms in exactly 12 g of 12c. A mole counts atoms or molecules, not mass or volume directly (although both are important). We can measure the relative masses of atoms. That is, the mass of a carbon-12 atom is twelve times the mass of an h-1 atom, and that the atom with the least mass is 1h. This suggests that a unit which has a value of one for 1h atoms and a unit of twelve for 12c atoms might be a candidate. The si unit for the (gram) mole is the number of c atoms in exactly 12 grams of 12c. This means that there are the same number of atoms in 1 gram of 1h as in 12 grams of 12c.

Related Questions

in part A the mass of empty tray was 2.78g
and the mass of tray with stopper was 38.82
the mass of the stopper is 38.82_2.78=36.04
we repeat this thing again with second type of observation and we get 39.2678_2.6409=36.6269
and the we did find the average
in part D we cut the glass and we use the bunse burner to make it smooth that was about 15 min
in Part E when the water was boiling poiling chips were moving a lot and there was so much steam
and then the sodium chloride became powder and a little bit salt
in part F when we mix the sodium iodid and the lead nitrate the mixture became yellow and when we did the filtration the yellow stay on the filter paper but all the water came down
plzzz i need three paragraphs conculsion and i need the answers for the last pictures

Atoms can bond to other atoms to make molecules. Atoms sometimes break these bonds and form them in a different way. For example, it is possible to take two molecules of hydrogen (H_2) and one molecule of oxygen (O_2), put them near one another, give them a little spark to help them start a reaction, and you will end up with two molecules of water (H_2O). Do you see what happened? Some of the H-H bonds and the O-O bonds broke and were replaced by O-H bonds. The process of forming or breaking bonds is called a chemical reaction. Chemical reactions come in a vast variety of types. But they typically involve energy changes that are, very roughly, 5 times 10^-19 J per molecule. We can use that number to estimate some useful quantities. Be sure to write your units in the answers below. Gasoline is made up of molecules with carbon and hydrogen (C and H). There are many kinds of molecules in a typical gasoline; but let's assume that all of them are in the form of C_8H_17. That substance has a mass of 18 times 10^-26 kg per molecule. If the mass density of gasoline is 720 kg/m^3, then how many molecules are in one gallon of gasoline? (1 m^3 = 264 gallons.) Please show your work and don't just look it up on the web. Here's a keep track of your units. At the end, the units should cancel out and your answer for the number of molecules should have no units. When you burn gasoline, you convert chemical energy to heat or work (to make your car move). If, when you burn gasoline, you convert 5 times 10^-19 J per molecule, how much energy can be obtained from one gallon of gasoline? If your car has a mass of 1,000 kg, then how much energy is needed to make your car go from rest to 65 mph (29 m/s)? (Think of this using kinetic energy. Ignore friction with the air or road.) How many gallons of gasoline are needed to make your car go from rest to 65 mph (29 m/s). (This is a rough estimate, neglecting the energy lost to air friction, heat, and other things.) If gasoline costs $2.20 per gallon, how much money does your answer to part (d) cost ?

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 â 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 + O2â 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 â 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, â PbO + 02 C. Ca + H2O â 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

CHE 1110 Lecture Notes - Lecture 4: Stoichiometry, Ionic Compound, Significant Figures

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