What is the chemical formula for water?

Which of the following is an element?

The atomic number represents the number of:

What is the SI unit for measuring the amount of substance?

Which property depends on the amount of substance present?

The chemical formula for sodium chloride is:

What is the mass number of an atom?

Which separation technique uses differences in boiling points?

Isotopes of an element have the same number of _____ but different numbers of _____.

The chemical formula for carbon dioxide is:

Which of the following is a compound?

What does the empirical formula represent?

Avogadro's number is approximately:

Which property can be observed without changing the substance's identity?

The formula for methane is:

Why is density considered an intensive property?

What is the main difference between elements and compounds?

How do homogeneous and heterogeneous mixtures differ?

What happens to the properties of elements when they form compounds?

Why can mixtures be separated by physical means?

What does it mean when measurements are precise but not accurate?

How does the molecular formula relate to the empirical formula?

Why do isotopes of the same element have similar chemical properties?

What makes a substance a pure substance?

How does chemical change differ from physical change?

Calculate the molar mass of H₂SO₄ (H=1, S=32, O=16):

How many moles are in 36 grams of water (H₂O, molar mass = 18 g/mol)?

If a compound contains 40% C, 6.7% H, and 53.3% O by mass, what is its empirical formula?

Balance the equation: ___Al + ___O₂ → ___Al₂O₃

A sample has a mass of 25.0 g and volume of 5.0 mL. What is its density?

How many atoms are in 2 moles of carbon?

What is the percent composition of oxygen in CO₂ (C=12, O=16)?

Which separation method would best separate sand from salt water?

If the empirical formula is CH₂O and the molar mass is 180 g/mol, what is the molecular formula?

How many grams are in 0.5 moles of NaCl (Na=23, Cl=35.5)?

A student measures the melting point of a substance five times (78.1°C–78.4°C) vs accepted value 80.0°C. The measurements are:

Compare data: Substance A: MP varies 75–85°C, visible particles. Substance B: MP exactly 78.2°C, uniform. Conclusion?

A compound contains 2.0 g H and 16.0 g O. If water contains 11.1% H and 88.9% O, is this compound water?

A mixture contains iron filings, salt, and sand. Most efficient separation sequence?

Two isotopes of carbon: C-12 has 6p + 6n, C-14 has how many neutrons?

A student claims that all mixtures can be separated by distillation. Evaluate:

Evaluate reliability of using density to identify a substance:

A lab balance measures ±0.001 g. True mass 5.000 g, reported 4.998 g. Evaluate measurement:

Critique this approach: 'To find empirical formula, I’ll burn the compound and measure mass lost.' Flaw?

Evaluate: 'The molecular formula is always more informative than empirical formula.'

Which single test would be most essential to distinguish salt (NaCl) vs sugar (C₆H₁₂O₆)?

To separate oil, water, and iron filings, which combination of techniques?

To determine both empirical and molecular formula of an unknown compound, which data needed?

A pharmaceutical company needs QC for aspirin tablets. Which approach is best?

Design a classification system to identify an unknown substance. Best sequence?