Sig Figs
Calculate the following problem and round to the correct number of significant figures.
3.24 + 7.0 = ?
10.2
Convert 25 inches to cm (1in=2.54cm)
64 cm
The decomposition of 20.0 g of water (H2O)
results in 18.0 g of oxygen (O2) and 2.0 g of
hydrogen (H2). What is the oxygen-to-hydrogen mass ratio?
9:1
Calculate the Molecular Weight of:
CH2
14.0266 g/mol
Identify the Atom/Ion:
Atomic number: 52
Mass number: 128
Tellurium
Calculate the following problem and round to the correct number of significant figures.
3.24 x 7.0 = ?
23
Convert 0.53 kilograms to grams (1kg=1000g)
53000g
Sample 1: 15.0g of hydrogen and 12.0g oxygen
Sample 2: 2.0g of hydrogen and 32.0g of oxygen
What is the oxygen-to-hydrogen mass ratio in each of the two samples?
Sample 1: 8:1
Sample 2: 16:1
Calculate the Molecular Weight of:
C4H6
54.088 g/mol
Identify the Atom/Ion:
Mass #: 88
Strontium
Calculate the following problem and round to the correct number of significant figures.
713.1 - 3.872 = ?
709.2
Convert 5.2 miles to inches (1mi=5280 ft, 1ft=12in)
329,472 in
OR
3.3 x 10^5 in
Two samples of CO2 are decomposed.
Sample 1 produces: 25.6g of oxygen and 9.60g of carbon
Sample 2 produces: 21.6g of oxygen and 8.10g of carbon
Are these results consistent with the law of definite proportions? Why?
Yes!
mass O / mass C = 25.6g/9.60g = 2.67
mass O / mass C = 21.6g/8.10g = 2.67
Calculate the Molecular Weight of:
NaOH
39.997 g/mol
Identify the Ion AND it's charge:
11 protons
12 neutrons
10 electrons
Sodium +1
Calculate the following problem and round to the correct number of significant figures.
710 / 3.0 = ?
240
Convert 7.58 centimeters to nanometers (1m=10^2cm, 1m=10^9nm)
7.58 x 10^7 nm
Nitrogen dioxide (NO2) contains 2.28g of oxygen for every 1.00g nitrogen
Nitrous Oxide (N2O) contains 0.570g of oxygen to every 1.00g nitrogen.
Is this consistent with the aw of multiple proportions? Why?
Yes!
(mass O to 1g N) / (mass N to 1g O)
228/0.570 = 4.00
Calculate the Molecular Weight of:
H2SO4
98.077 g/mol
Identify the Ion AND charge:
13 protons
14 neutrons
10 electrons
Aluminum +3
Calculate the following problem and round to the correct number of significant figures.
(12.4 x 7.943) + 0.0064 = ?
98.5
Convert 3.44 milligram per second to kilogram per hour (1mg=10^-3g , 1kg=10^3g)
0.0124 kg/hr
OR
1.24 x 10^-2 kg/hr
A 1.0g sample of hydrogen reacts completely with 19.0g of fluorine to form a compound of hydrogen and fluorine (HF).
H+F---> HF
1) What is the percent by mass of each element in the compound?
2) What mass of hydrogen would be present in a 40 gram sample of this compound?
1) 5% Hydrogen, 95% Fluorine
2) 0.05x40= 2.0g
Calculate the Molecular Weight of:
(NH4)2CO3
96.09 g/mol
Given Fe2+, how many electrons and neutrons does it have?