Scientific Notations
Write 5,000 in scientific notation.
5.0×103
Which element has the highest electronegativity on the periodic table?
Flourine
Using the reaction 2H2(g)+O2(g)→2H2O(g) , if 4.00 moles of H2 react with excess O2, how many moles of H2O form?
4.00 moles of H2O
Convert 2500 cm to meters?
25 m ( 1m=100 cm)
What do we call the maximum amount of solute that can dissolve in a solvent at a given temperature?
Solubility
Write 0.00072 in scientific notation
7.2×10-4
As you move left to right across a period, what happens to atomic radius?
What happens to the electronegativity going left to right?
- Atomic radius decreases
- EN increases
For 2Na(s)+Cl2(g)→2NaCl(s): starting with 10.0 g Na and excess Cl2, what mass of NaCl is produced? (Mm: Na = 22.99g/mol, NaCl = 58.44 g/mol)
25.4 g NaCl
How many moles are in 5g of NaCl? (Molar mass Na = 22.99, Cl = 35.45 → NaCl = 58.44 g/mol)
0.0856 moles
True or False: Most gases become more soluble in water as temperature increases.
Support your answer with why?
False- They become less soluble, due to the gas molecules moving at faster speeds and further apart allowing them to escape the liquid more easily instead of staying trapped in the water.
Multiply (6.2×105)×(3.0×10-8)
18.6×10-3
Which has the larger radius: Na or Na⁺?
Explain why?
Na (neutral sodium) has the larger radius
- The Na⁺ ion loses an electron shell, making it much smaller.
Given N2(g)+3H2(g)→2NH3(g). If you start with 5.00 g N2 and 12.0 g H2, which is the limiting reagent? (Mm: N2=28.0 g/mol, H2=2.016 g/mol)
N2 limiting reagent
Convert 12.0 m/s to kilometers per hour (km/h)
43.2 km/h
1km= 1000 m
1h=3600 s
Which compound is more soluble in water: NaCl (table salt) or AgCl (silver chloride)?
NaCl because AgCl is mainly insoluble
Explain why scientific notation is especially useful in fields like astronomy or microbiology.
These fields deal with extremely large distances (like light-years) or extremely small measurements (like virus diameters). Scientific notation allows scientists to express these numbers concisely and avoid errors from writing out many zeros.
Why does ionization energy generally increase across a period from left to right?
Because as you move across a period, the nucleus gains more protons while electrons are added to the same energy level. This stronger attraction makes it harder to remove an electron, so ionization energy increase
Why must chemical equations be balanced before using them in stoichiometry problems?
Because of the law of conservation of mass — atoms cannot be created or destroyed in a chemical reaction. Balancing ensures the number of each atom is the same on both sides, which makes mole ratios valid for calculations
A sample of aluminum has mass 1350 g. Given the density of aluminum is 2.70 g/cm3, what is the volume in liters?
0.500 L
1L=1000 cm3
What type of solution is formed when you dissolve more solute than the solvent can normally hold at that temperature?
Supersaturated solution
Why is it important to keep the coefficient in scientific notation between 1 and 10? What happens if it isn’t?
Scientific notation requires 1 ≤ coefficient < 10 to standardize numbers and make them easy to compare. If the coefficient is outside this range, the number isn’t in proper scientific notation and can cause confusion in calculations. For example, 50×103 should be written as 5.0×104.
Oxygen has a higher electronegativity than sulfur, even though both are in the same group. Explain why.
Oxygen is smaller (fewer electron shells), so its valence electrons are closer to the nucleus and feel a stronger attraction. Sulfur has more electron shielding, which reduces the pull on bonding electrons, making its electronegativity lower than oxygen’s.
In a reaction, the limiting reagent is completely consumed first. What does this mean for the other reactants like what are they called, and why is the limiting reagent the only one used to calculate product amounts?
The other reactants are left in excess (they are not fully used up). The limiting reagent “limits” the reaction because once it’s gone, the reaction stops and no more product can form. That’s why product yield is always based on the limiting reagent.
The density of liquid ethanol is 0.789 g/mL. How many molecules of ethanol are in 250 mL of ethanol?
(Molar mass of ethanol = 46.08 g/mol, Avogadro’s number = 6.022×1023 molecules/mol)
2.58×1024 molecules of ethanol
According to solubility rules, will BaSO4 dissolve significantly in water? Why or why not?
No- because most sulfates are soluble but BaSO4 this is an exception to the rule.