CHEM 1031 Study Guide - Midterm Guide: Antoine Lavoisier, Unified Atomic Mass Unit, Noble Gas

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1. 2: scientific laws describe how nature behaves they are generalizations about what nature does, scientific laws describe how nature behaves they are generalizations about what nature does. 1. 7: scientific measurements are reported so that every digit is certain except the last, which is estimated. In any reported measurement, the non-place-holding digits those that are not simply marking the decimal place are called significant figures (or significant digits). The greater the number of significant figures, the greater the certainty of the measurement: exact numbers have no uncertainty, and thus do not limit the number of significant figures in any calculation, units raised to a power. In a chemical reaction, atoms change the way that they are bound together with other atoms to form a new substance. 2. 7: an average mass called the atomic mass for each element, 1 mol = 6. 0221421 * 1023 particles, the mass of 1 mol of atoms of an element is the molar mass.

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I need help doing my lab homework, I missed lab that day because, I was sick and it's due.

Chemical Reactions and Equations Learning objectives To observe physical and chemical properties associated with chemical changes To be able to give evidence for the occurrence of a chemical reaction To write a balanced chemical equation To identify areaction as a combination, decomposition, precipitation, single or double replacement, or combustion reaction ntroduction When a substance undergoes a physical change, it changes its appearance but not its composition. For example, when ice melts to form water, it undergoes a physical change from solid to liquid. In a chemical change, the composition of a substance is changed to give a new substance with different physical and chemical properties. For example, when silver tarnishes, the shiny silver (Ag) changes to a dull gray silver sulfide (AgaS). Not only has the chemical formula changed from Ag to Agus, but also the physical properties (shininess) of the substance have changed. Some examples of physical and chemical changes are listed in Table 1 below. Table 1. Comparison of Physical and Chemical Changes Examples of Physical changes Examples and Evidence of Chemical Changes Change in state (melting, freezing, evaporating Formation of a gas (bubbles) subliming) Formation of a solid (precipitate) Change in size Tearing Change in Color Heat is given off or absorbed A solid dissolving in a solvent In a chemical reaction, atoms in the reactants are rearranged to produce new combinations of atoms in the products. However, the total number of atoms of each element in the reactants is equal to the total number of atoms in the products. This is true according to the Law of Conservation of Mass, which states that the total mass remains constant during a chemical reaction. In other words, matter cannot be created or destroyed in a chemical reaction. In a chemical equation, the reactants are shown on the left and the products are on the right. An arrow in between indicates that a chemical reaction occurs. Finally, the physical state of each compound is designated in parentheses after the chemical formula. Solid, liquid, gas, and aqueous (dissolved in water) are shown as(s,(n,(g), and (aq), respectively.

1.Which of the following is a physical property?

A) ozone reacts with silver to give silver oxide

B) platinum metal does not react with hydrochloric acid

C) the density of lead

E) Sulfur burns in oxygen to form sulfur trioxide

2. Which of the following is a chemical property of gold?

A) is malleable

B) does not react with hydrochloric acid

C) is a good conductor of heat

D) is a good conductor of electricity

3) Which of the following is a physical change?

a) the freezing of water to form ice

B) the inability of gold react with water

C) the burning of paper

D) the sodium metal vigorously with water

E) the reaction of zinc with hydrochloric acid

4. Which one of the following would be classified as a heterogenous mixture?

A) copper nitrate solution

B) mix of table salt and black pepper

C) Salt water

D)brass

E) a sugar solution

5. Which of the following is a chemical change?

A) the boiling of water to form steam

B) crushing of lump of sulfur into yellow powder

C) the reaction of chlorine gas and sodium to form salt

E) hammering zinc into a thin film

6) An extensive property is

A) independent of the quantity of matter observed

B) difficult to measure

C) always strongly dependent on the external conditions

D) dependent on the quantity of matter observed

E) is a unique value regardless of the measurement conditions

7) Which of the following defines or expresses the concepts of accuracy?

A) average of the data

B) differences between the accepted answer and the average value of the data

C) deviation of the average

D) the closest value to the expected answer

E) reproducibility of a measurement

8) Hydrates are:

A) orgainc compounds that contain oxygen together with usual carbon and hydrogen

B) readily soluble in water and release energy

C) concentrated solutions of salts in water

D) moistyre sensitive hygroscopic inorganic salts

E) compounds in which each formula unit has one or more water molecules associated with it

9) Which of the following is the correct defintion of isomer?

A) Isomers are molecules with the same empirical formula but have different isotopes

B) Isomers are molecules that have the same molecular formula but contain different istotopes.

C) Isomers are molecules that have the same molecular formula but different arrangement of atoms in space

D) Isomers are molecules that have the same arrangements of atoms in space but different empirical and molecular formulas

E) Isomes are molecules that have the same empirical formula but different arrangements of atoms in space

10) Most water-soluble compounds of Group 1A or 2A elements are:

A) nonelectrolytes

B) weak electrolyes

C) weak acid

D) strong electrolytes

E) strong acids

11) to precipitate Cd2+(aq) from solution one could add:

A) KI(Aq)

B) NaCl(aq)

C) H2S(aq)

D)HNO3(aq)

E) HCl(aq)

12) Select a statement that best describe the oxidation process

A) in the oxidation process all elements experience an increase in oxidation state

B) in the oxidation process all elements change oxidation state

C) in the oxidation process some elements change their oxidation state

D) in the oxidation process some elements experience oxidation state increase

E) In the oxidation process only oxygen increases its oxidation state.

13. A disproportionation reaction is one in which:

A) the dame substance is oxidized and reduced

B) the equation is not balanced

C) both reactants are reduced

D) water must be added

C) more of one substance reacts than another

14) The energy of molecules of a gas:

A) is the same for all molecules at constant temperture

B) is dependent on concentration

C) increases with an increase in pressure

D) is distributed over a wide rande at constant temperature

E) increase with a decrease in temperture

15. The volume correction term in the van der Waals equation is present because:

A) molecules occupy volume

B) molecules attract each other

C) barometers are inaccurate

D) molecules repel each other

E) molecules are diatomic

Decomposition of Malachite

Here is what Malachite is Made Out Of

Malachite is a famous and very popular semi-precious stone. Its banded light and dark green bands are one-of-a-kind, and give it a unique ornamental quality unlike that of any other stone. The light and dark green bands are so distinctive that malachite may be one of the most easily recognized minerals by the general public. Malachite is popular in jewelry, especially Native American southwestern jewelry. The stones inlayed in silver make a nice alternative to traditional turquoise jewelry.

Malachite is a form of copper carbonate with the molecular formula Cu₂CO₃(OH)₂. When heated to around 200 ï¿½C, malachite decomposes into copper (II) oxide (CuO) and other products.

Reaction Stoichiometry

The Law of Conservation of Mass states that matter can neither be created nor destroyed. Therefore, the number of atoms of each element on the reactants side must be same as the number of atoms on the products side. This quantitative study of chemical reactions is called stoichiometry. The substances in a balanced reaction are related to each other by stoichiometric molar ratios. For example, magnesium reacts with hydrochloric acid in a 1:2 stoichiometric ratio in the balanced equation below.

Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)

The molar ratios can be used as conversion factors to find the amount (in moles) of one substance given the amount of another. For example, given the number of moles of HCl, the amount of MgCl₂ can be determined as shown below.

nMgCl2=nHCl x (1mol MgCl2) / (2mol HCL)

The molar ratios are used to determine the amount in moles. However, the amount of reactant or product is often measured in grams. Mass can be converted to moles and vice versa as shown below.

n = m / (MM)

m = n x MM

where n is the number of moles, m is the mass of the product in g, and MM is its molar mass in g/mol.

To observe the Law of Conservation of Mass, you can perform different types of chemical reactions. For example, you can use a decomposition reaction to observe one compound being broken down into two or more elements or new compounds. For this reaction to take place, you must break existing bonds within the starting compound. Different sources of energy such as heat, light, or electricity may be used. Through a decomposition reaction, you can observe that the atoms in the original compound are not destroyed but are rearranged to form simpler substances, such as elements or compounds.

About This Lab

In this lab, you will test if the relationship between malachite and copper (II) oxide is stoichiometric. To do this, you will heat a known mass of malachite to produce copper (II) oxide. You will then compare the amount of copper (II) oxide obtained experimentally with the amount of copper (II) oxide expected from the balanced equation for the decomposition reaction.

1.Take a crucible from the Containers shelf and place it on the workbench.

2.Take a balance from the Instruments shelf and place it on the workbench.

3.Move the crucible onto the balance. Record the mass of the empty crucible to the nearest 0.001g in your Lab Notes.

4.Move the crucible onto the workbench.

5.Take copper (II) carbonate hydroxide from the Materials shelf and add 10 g to the crucible.

6.Move the crucible onto the balance and record the mass of the crucible containing copper (II) carbonate hydroxide in your Lab Notes.

7.Take a Bunsen burner from the Instruments shelf and place it on the workbench.

8.Move the crucible onto the Bunsen burner.

9.Double-click on the crucible to open its properties. Select Show Contents and click OK. This gives you a cut-away view of the crucible's contents.

10.Turn the Bunsen burner on to low flame by clicking the knob at the bottom once. Clicking multiple times will increase the intensity of the flame until it is turned off.

11.Watch the crucible until the malachite fully decomposes. You will see a distinct color change.

12.Move the crucible onto the workbench to cool.

13.Turn off your Bunsen burner.

14.Weigh the crucible with its contents and record the mass to the nearest 0.001 g in your Lab Notes.

Clear your station.

Lab Notes:

Numbers below refer to numbers in the above âAbout this Labâ

3. Empty crucible = 88 g

5. Added 10 g of Copper (II) carbonate hydroxide to crucible

6. Crucible with Copper (II) carbonate hydroxide = 98 g

11. to Black

14. after heating crucible with its contents = 95.195

Questions I have answered:

How many grams of malachite did you add to the crucible? 10g

How many grams of product were in the crucible after heating? 7.195

By how much did the mass of the crucible's contents change after heating? -2.805

The molar mass of malachite is 221.1 g/mol. How many moles of malachite were present before the reaction? 0.04523 mol

The product remaining in the crucible after heating is copper (II) oxide. The molar mass of copper (II) oxide is 79.55 g/mol. How many moles of copper (II) oxide were produced during the reaction?

0.0945 mol

Please answer the following:

Q1 a. Which of the following represents the balanced chemical equation for this reaction?

Cu2CO3(OH)2=2CuO+H2O

Cu2CO3(OH)2=CuO+CO2

Cu2CO3(OH)2=2CuO+H2O+CO2

Cu2CO3(OH)2=CuO+H2O+CO2

b. Based on the number of moles of malachite that you started with, how many grams of water were produced? The molar mass of water is 18.0153 g/mol. Choose the closest answer.

1.815 g 0.8148 g 1.630 g 1.982 g

c. Based on the number of moles of malachite that you started with, how many moles of CO₂were produced? Choose the closest answer.

1.000 mol 0.04523 mol 0.9000 mol 0.09045 mol

d. Based on the number of moles of malachite that you started with, how many grams of CO₂were produced? The molar mass of CO₂ is 44.01 g/mol. Choose the closest answer.

1.991 g 0.4401 g 0.04523 g 3.981 g

Q2a. Based on the number of grams of CO₂ and H₂O produced during the reaction, does this compensate for the observed loss of mass?

A. No, because this violates the law of conservation of mass

B. yes, this compensates for the mass lost in the reaction

C. No, because more copper oxide was produced

D. No because mass is conserved

b. You observed that the products in the crucible weigh less than the reactants that you added. How is this possible?

A. Mass was lost due to experimental error

B. The Malachite absorbed CO2 from the air

C. CO2 and H2O were released as gases

D. Mass was converted to energy

c. What kind of a reaction took place upon heating?

A. decomposition

B. single displacement

C. synthesis

D. Double displacement

d. Baking soda is used as a leavening agent in baking. When heated, baking soda undergoes a decomposition reaction to form carbon dioxide. Given the data below, which of the following reactions occurs during baking? The molar mass of baking soda is 84.007 g/mol and the molar mass of carbon dioxide is 44.01 g/mol.

Mass of empty crucible (g) = 55.000

mass of crucible with baking soda (g) = 57.000

mass of crucible and contents after the reaction (g) =56.260

A. 2NaHCO3= 2Na+2CO2 +H2O

B. 2NaHCO3 = Na2O + 2CO2 +H2O

C. NaHCO3 = NaOH +CO2

D. 2NaHCO3 = Na2CO3 + CO2 +H2O

CHEM 1031 Study Guide - Midterm Guide: Antoine Lavoisier, Unified Atomic Mass Unit, Noble Gas

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