Chapter Assessment Answer Key Chemistry: Matter and Change T167 4 CHAPTER ASSESSMENT Date alpha radiation Dalton’s atomic theory radiation radioactivity Chapter Assessment particles involved in a reaction. Chemistry: Matter and Change • Chapter 4 nucleus. A nuclear equation shows the atomic number and mass number of the 19 Both concern changes in atoms. A nuclear reaction involves a change in an atom’s 15. nuclear reaction, nuclear equation atom. in the nucleus of a given atom.
A) Water is 11% hydrogen and 89% oxygen by mass. B) Water boils at 100°C at 1 atm pressure. C) Water can be separated into other substances by a chemical process. D) Water and salt have different boiling points. E) Water is a compound.
 Precision: measure of how close a series of measurements are to one another.  Accepted Value: the correct value based on reliable references  Experimental Value: the value measured in the lab.  Error: o Error = experimental value – accepted value  Percent error: o Percent Error = |error| x 100% Accepted value  Significant Figures: all of the digits that are known, plus a last digit that is estimated. o
(2 points) Mg(s) + 2 HCl(aq) → H2(g) + MgCl2(aq) 2. Determine the partial pressure of the hydrogen gas collected in the gas collection tube. (3 points) partial pressure H2 = total pressure - vapor pressure of water = 746mmHg - 19.8mmHg = 726mmHg 3. Calculate the moles of hydrogen gas collected. (4 points) n = 125 4.
The following data were obtained when a sample of barium chloride hydrate was analyzed as described in the Procedure section. Calculate (a) the mass of the hydrate, (b) the mass of water lost during heating, and (c) the percent water in the hydrate. Mass of empty test tube 18.42 g Mass of test tube and hydrate (before heating) 20.75 g Mass of test tube and anhydrous salt (after heating) 20.41 g. Mass of the Hydrate is 2.33g. Loss (H2O) is 0.34g. Percent H2O in Hydrate is equal 0.34/2.33=14.6% 3.
The components of the sample will be separated on the basis of their ranging physical and chemical properties, imparting different affinities for the two phases. Thin layer chromatography (TLC) was the first chromatographic method for assessing phospholipids, and is commonly used today.
3 x (C H5 N) = C3H15N3 Hydrated compounds Solving process: 1st- the difference between the initial mass and that of the dry sample is the mass of water that was driven off. Mass of hydrate minus mass of dry sample equals the mass of water 10.407 – 9.520 = 0.887 g 2nd- The mass of dry BaI2 and the mass of water are converted to MOLES. 9.520 g BaI2 x 1 mol BaI2 ∕ 391 g BaI2 = 0.0243 mol BaI2 anhydrate 0.887 g H2O x 1 mol H2O / 18.0 g H2O = o.o493 mol H2O 3rd: Dividing both results by the amt of 0.0243 mol, we get a ratio of 1 to 2.03, or 1 to 2, since the formula must have full numerical integers of water molecules, in other words no fractions of a water molecule. Thus, for every 1 mole of BaI2, there are two moles of water. The formula for the hydrate is written as BaI2 • 2H2O And it is named barium iodide dihydrate.
Since this reaction involves a dramatic color change, it can be used in a titration experiment. Here is the net ionic equation: 12 H+ (aq) + 4 MnO4– (aq) + 5 C2H5OH (aq) ⎯→ 5 HC2H3O2 (aq) + 4 Mn2+ (aq) + 11 H2O (l) deep purple almost colorless 1.00 mL of a white wine was added to excess sulfuric acid solution, then titrated with a 0.100 M KMnO4 solution. It took 20.4 mL of the KMnO4 solution to reach the endpoint. a) Which substance is oxidized, and which reduced, in the reaction? b) What is the molar concentration (molarity) of ethanol in the wine?
Calculate the molarity of the original vinegar solution and its concentration in gdm-3, given that it reacts with NaOH in a 1:1 ratio. 7. 2.5 g of a sample of ethanedioic acid, H2C2O4.nH2O, was dissolved in water and the solution made up to 250 cm3. This solution was placed in a burette and 15.8 cm3 were required to neutralise 25 cm3 of 0.1 moldm-3 NaOH. Given that ethanedioic acid reacts with NaOH
4. Using your definition of substance, classify the following as either a pure substance or a mixture a. ocean water b. air c. granite d. wood e. wine f. liquid nitrogen Part of studying chemistry is being able to form pictures in your mind of what matter looks like on an atomic or molecular level – picturing what kinds of atoms or molecules a particular substance is made of. We can classify the substance based on what types of atoms and molecules it’s made of. We use these images as a way of representing substances. Consider the drawings below: These images show methane molecules (CH4) in each of the three states of matter: solid, liquid, and gas.