Chem I
Midterm Exam Review Sheet
1. State the difference between a scientific law & scientific theory.
Scientific Law states what happens doesn’t explain
Scientific Theory explains why something happens
2. Define hypothesis.
An explanation for observations
3. List the steps of the scientific method.
Observation, hypothesis, test your experiment, revise hypothesis if necessary
4. Name three examples of matter.
air, smoke, dust
5. Distinguish between a physical change & a chemical change.
Physical: can be observed or measured without changing the chemical composition of the substance
Chemical: changes the substance into a new substance & the original substance can not be brought back
6. Contrast compounds & mixtures.
Compound: composed of 2 or more elements; pure substances; can’t be physically separated
Mixtures: can be separated physically; composition varies
7. Define chemical formula.
Shows the number & type of atoms present in a compound; the proportions of the atoms relative to each other
8. Determine the number of significant figures in the following:
a. 0.0030 b. 10907 c. 200 d. 1.087
a. 2 b. 5 c. 1 d. 4
9. What is the difference between accuracy & precision?
Accuracy closeness to the standard value
Precision: closeness between the measurements
10. Complete the following conversion.
a. 48 kg to g b. 34 km to m c. 23 mg to g d. 56 cm to km
a. 48kg x (1000g/1 kg) = 48000 g b. 34 km x (1000m/1 km) = 34000 km
c. 23 mg x (1g/1000 mg) = 0.023 g
d. 56 cm x (1m/100cm) x (1 km/1000m) = 0.00056 km
11. Calculate the density of an object with a mass of 3.40 x 102 g & a volume of 26 L.
D = m/v 3.4 x 102 / 26 L = 13 g/L
12. A mechanic needs to put tires on 10 cars. Each tire requires 3 lugnuts & each car needs 4 tires. How many lugnuts does the mechanic need?
10 cars x (4 tires/1 car) x (3 lugnuts/1 tire) = 120 lugnuts
13. Convert 12 cm/h to mm/sec
(12 cm/hr) x (1000mm/100cm) x (1 hr/3600s) = 0.033 mm/sec
14. Convert 15 g/L to kg/cm3
(15g/L) x (1kg/1000g) x (1000L/1kL) = 15 kg/kL
15. Who discovered the electron, proton, & neutron?
Proton: Rutherford Neutron: Chadwick Electron: Thompson
16. Compare the masses of the subatomic particles.
Protons & neutrons have the same mass (1.67 x 10-24 g)
Electrons are larger (9.11 x 10-28 g)
17. Define the atom, mass number, & atomic number.
Atom: smallest part of an element
Mass Number : number of protons & neutrons
Atomic Number: Number of protons; defines an element; can not change
18. Which element has the highest electronegativity? F
19. Complete the chart.
Element / Atomic # / Mass # / # Protons / # electrons / # neutronsNa / 11 / 23 / 11 / 11 / 12
Mg2+ / 12 / 24 / 12 / 10 / 12
Fe / 26 / 56 / 26 / 26 / 30
Cl- / 17 / 35 / 17 / 18 / 18
20. Define isotopes.
Different number of neutrons
21. Define binary, ternary, & polyatomic ions.
Binary: 2 elements Ternary: 3 or more elements
Polyatomic ions: A group of ions acting as a group & carry a charge
22. Identify each as a molecular or ionic compound.
a. NaCl I b. CCl4 M c.SO4 M d. FeCl3 I
23. Name the following:
a. HI b. Fe(OH)3 c. HNO (aq) d. K2CO3 e. H2SO4 (aq) f. NO
a. hydrogen iodide b. iron (III) hydroxide c. hyponitrous acid
d. potassium carbonate e. sulfuric acid f. nitrogen monoxide
24. List the prefixes & their value.
mono: one tetra: four hepta: seven deca: ten
di: two penta: five octa: eight
tri: three hexa: six nona: nine
25. Covert 6.9 x 1025 iron atoms to grams
6.9 x 1025 Fe atoms x (1 mol/6.02 x 1023atoms) x (56 g/1 mol) = 6,400 g
26. Convert 3.56 x 1023 sulfur molecules to moles.
3.56 x1023 molecules x (1 mol/6.02 x 1023atoms) = 0.60 mol
27. Convert 33 g of NaCl to moles.
33 g NaCl x (1 mol/ 58 g) = 0.57 mol
28. CO2 has a volume of 310 L at STP. What is the mass of CO2 ?
310 L CO2 x ( 1 mol/22.4 L) x (44 g/1 mol) = 609 g CO2
29. Calculate the % of each element in potassium sulfite. K2SO3
K: (80 g/160 g) x 100 = 50% O: (48 g/ 160 g) x 100 = 30%
S: (32 g / 160 g) x 100 = 20%
30. Identify the type of reaction, balance & predict the products.
a. potassium chloride è
2 KCl è 2 K + Cl2 Decomposition
b. hydrogen + oxygen è
2 H2 + O2 è 2 H2O Synthesis
c. sodium hydroxide + KCl è
NaOH + KCl è KOH + NaCl double replacement
d. barium nitrate + iron (III) chloride è
3 Ba(NO3)2 + 2 FeCl3 è 2 Fe(NO3)3 + 3 BaCl2 double replacement
e. tetracarbon octahydride + oxygen è
C4H8 + 5 O2 è 4 CO2 + 4 H2O combustion