In a flame test lab, sodium emits bright yellow light, while potassium gives violet. The ease of electron excitation in K is due to:

A chemist compares first ionization energies of Mg (738 kJ/mol) and Al (577 kJ/mol). The drop occurs because:

Which atom would MOST readily form a 2+ ion in ionic compounds?

In a semiconductor lab, an element with config [Ar]4s²3d¹⁰4p³ is used. Its electronegativity is expected to be:

A student claims oxygen has higher first IE than nitrogen because it has more protons. This is:

Which process requires the LEAST energy?

During electrolysis, a technician needs an element that easily loses electrons to form cations. Best choice:

An unknown element forms X³⁺ and has 3 valence electrons. It likely belongs to:

Why is atomic radius of Cl smaller than S?

A student mixes 2.0 mol H₂ and 1.0 mol O₂ to make water. After reaction, gas remaining is:

In a car airbag, 2NaN₃ → 2Na + 3N₂. To produce 67.2 L N₂ at STP, mass of NaN₃ needed is:

A lab prepares CO₂ using NaHCO₃ + HCl → NaCl + H₂O + CO₂. If 8.4 g NaHCO₃ (MM=84) is used, theoretical CO₂ is:

A student uses 5.0 g Mg and 5.0 g O₂ to make MgO. Limiting reactant is:

In 2Al + 3Cl₂ → 2AlCl₃, with 54 g Al and 213 g Cl₂, excess reactant mass left is:

A pharmaceutical chemist synthesizes aspirin. Theoretical yield = 10.0 g, actual = 7.8 g. % yield is:

Why might % yield exceed 100% in student labs?

In rocket fuel: N₂H₄ + O₂ → N₂ + 2H₂O. 32 g N₂H₄ (MM=32) requires ___ g O₂.

A student balances Cu + HNO₃ → Cu(NO₃)₂ + NO₂ + H₂O. Correct coefficients:

In 4NH₃ + 5O₂ → 4NO + 6H₂O, 4 mol NH₃ produces ___ mol H₂O.

A chemist notes that Be resists oxidation more than B. Reason:

Across Period 2, which property increases NON-uniformly due to electron repulsion?

Which pair violates periodic EN trend?

A student measures atomic radii: Ca > Mg > Be. This illustrates:

An element with high IE, high EN, and small radius is likely a:

th high IE, high EN, and small radius is likely a:

In NH₃ synthesis, excess N₂ is used to:

A student recovers 3.2 g Cu from 4.0 g CuO using H₂. % yield is: (MM Cu=64, CuO=80)

Which reaction has 1:1 mole ratio of reactants?

A technician uses 10 g CaCO₃ to produce CO₂. Max CO₂ (g) is: (MM CaCO₃=100)

In 2KClO₃ → 2KCl + 3O₂, 245 g KClO₃ (MM=122.5) gives ___ L O₂ at STP.

Which ion is smaller than its parent atom?

Why does He have higher IE than H?

EN of Si is ~1.8, P is ~2.1. This supports:

An element with config [Kr]5s²4d¹⁰5p³ is in:

A student uses 6.9 g Na and 7.1 g Cl₂. Limiting reactant? (MM Na=23, Cl₂=71)

Theoretical yield = 50 g, actual = 45 g. % yield =

In C + O₂ → CO₂, 12 g C requires ___ g O₂.

Which requires balancing by fractional coefficients?

Mass of Al to produce 3.36 L H₂ at STP (2Al + 6HCl → 2AlCl₃ + 3H₂):

2.0 mol Fe reacts with 2.0 mol Cl₂ → FeCl₃. Product moles =

Down Group 17, reactivity decreases because:

Which oxide gives alkaline solution in water?

A sudden jump in IE after 3rd removal suggests:

In Fe₂O₃ + 3CO → 2Fe + 3CO₂, 160 g Fe₂O₃ produces ___ g Fe.

Actual yield < theoretical due to:

Which has highest IE in Period 2?

EN difference >1.7 usually indicates:

Why is Ar’s atomic radius larger than Cl’s?

In Ba + Cl₂ → BaCl₂, 137 g Ba + 71 g Cl₂ → product mass =

A student gets 8.5 g MgO from 4.8 g Mg. % yield? (MM Mg=24, MgO=40)

Which element would least likely form an anion?

In combustion of ethanol: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O. 46 g ethanol gives ___ g H₂O.

Atomic radius trend explains why:

Which is NOT a periodic property?

In 2H₂S + 3O₂ → 2SO₂ + 2H₂O, 34 g H₂S (MM=34) requires ___ g O₂.

A student calculates 10 g product, gets 12 g. Likely error:

Why is O²⁻ larger than F⁻?

In Zn + 2HCl → ZnCl₂ + H₂, 6.5 g Zn (MM=65) gives ___ L H₂ at STP.

Which has lowest EN?

A sudden drop in IE between Group 2 and 13 is due to: