What numerical expression gives the number of moles in 8.5g of H₂O?

• $8.5g\times\frac{1\ mol}{18g}$

• $18g\times\frac{1\ mol}{8.5g}$

• $8.5g\times\frac{18g}{1\ mol}$

• $18g\times\frac{8.5g}{1\ mol}$

Tags

NGSS.HS-PS1-7

The mass spectrum represented above is most consistent with which of the following elements?

• Os

• W

• Re

• Ta

Tags

NGSS.HS-PS1-1

Ca²⁺(aq) + CO₃^2-(aq) → CaCO₃(s)

A student obtains a 10.0g sample of a white powder labeled as CaCl₂. After completely dissolving the powder in 50.0mL of distilled water, the student adds excess Na₂CO₃(s), which causes a precipitate of CaCO₃(s) to form, as represented by the equation above. The student filters the CaCO₃(s), rinses it, and dries it until its mass is constant. Which of the following scientific questions could best be answered based on the results of the experiment?

• Is the Na₂CO₃(s) used in the experiment pure?

• Is the CaCl₂(s) used in the experiment pure?

• What is the molar solubility of CaCl₂ in water?

• What is the molar solubility of CaCO₃ in water?

A jar labeled KF contains a powder. The table above contains information determined by analyzing a sample of the powder in the laboratory. What information in the table is the most helpful in determining whether the powder is pure KF?

• Mass

• Mass Percent of K

• Density

• Color

Tags

NGSS.HS-PS1-3

Which of the following is the correct electron configuration for a ground-state atom of Sulfur?

• 3p⁴

• 1s²2s²2p⁶3p⁴3s²

• 1s²2s²3s²3p⁴

• 1s²2s²2p⁶3s²3p⁴

Tags

NGSS.HS-PS1-1

Which peak represents the 2s subshell?

• X

• Y

• Z

Tags

NGSS.HS-PS1-1

The atomic radii of the elements in the oxygen group in the periodic table are given in the table above. Which of the following best helps explain the trend of increasing atomic radius from O to Po?

• The number of particles in the nucleus of the atom increases.

• The number of electrons in the outermost shell of the atom increases.

• The attractive force between the valence electrons and the nuclei of the atoms decreases.

• The repulsive force between the valence electrons and the electrons in the inner shells decreases.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Na reacts with Cl in a mole ratio of 1 to 1, forming the ionic compound NaCl. Which of the following elements will react with Cl in a mole ratio of 1 to 1, forming an ionic compound, and why?

• S, because it is in the same period as Cl.

• Mg, because the atomic mass of Mg is similar to that of Na.

• K, because it is in the same period as Na.

• K, because it is in the same group as Na.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

A 1.0 mol sample of which of the following compounds has the greatest mass?

• CO

• H₂O

• AgCl

• NO₂

The mass spectrum represented above is most consistent with which of the following elements?

• Zr

• Ti

• Y

• Mo

Tags

NGSS.HS-PS1-1