Preap Chemistry

Two charges, Q1 and Q2, exert an energy of repulsion when separated by a distance, d.  Two larger charges, Q3 and Q4, are separated by the same distance, d.  How does the energy of repulsion between Q1 and Q2 compare to the  energy of repulsion between Q3 and Q4? 

• Energy of repulsion is the SAME, because the distance separating each pair of charges is the SAME.
• Energy of repulsion between Q1 and Q2 is SMALLER, because the charge of Q1 and Q2 is SMALLER.
• Energy of repulsion between Q1 and Q2 is LARGER, because the charge of Q1 and Q2 is LARGER. 
• Energy of repulsion between Q1 and Q2 is SMALLER because the charge of Q1 and Q2 is LARGER.

Tags

NGSS.HS-PS2-4

Two charges Q1 and Q2 exert an energy of attraction when separated by a distance, d.  Those same charges are then separated by a larger distance, 2d.  What will happen to the energy of attraction between the two charges? 

• The energy of attraction will remain the SAME, because the charges are the SAME.
• The energy of attraction will INCREASE, because the distance over which the charges must attract INCREASES.
• The energy of attraction will DECREASE, because the distance over which the charges must attract INCREASES.
• The energy of attraction will DECREASE, because the distance over which the charges must attract DECREASES.

Tags

NGSS.HS-PS2-4

Which of the following postulates of Dalton's atomic theory are NO longer true?

• 2 ONLY
• 2 and 3 ONLY
• 4 ONLY
• ALL postulates remain true today.

Tags

NGSS.HS-PS1-7

Thomson used a cathode ray tube, which is a vacuum-sealed tube with a cathode and anode on one end that creates a beam of particles traveling towards the other end of the tube.  Based on the image and your understanding of Thomson's experiment, what is the likely charge of the particle Thomson discovered?

• The particle is NEGATIVELY charged.  The particle is attracted to the POSITIVE plate.
• The particle is NEGATIVELY charged.  The particle is attracted to the NEGATIVE plate.
• The particle is POSITIVELY charged.  The particle is attracted to the POSITIVE plate.
• The particle is POSITIVELY charged.  The particle is attracted to the NEGATIVE plate.

Tags

NGSS.HS-PS1-3

The discovery and characterization of cathode rays was important in the development of the atomic theory because 

• it indicated that all matter contains protons. 
• it indicated that all matter contains alpha particles.
• it led to the suggestion of the existence of the neutron. 
• it indicated that all matter contained electrons.

Rutherford’s α-scattering experiment showed that most α particles directed toward a thin metallic foil passed through with only slight deviations. From this evidence we can conclude that

• the mass of the atom is concentrated in a very small area.
• α particles are too small to hit anything.
• the foil was too thin.
• α particles are uncharged

In a neutral atom of ¹⁹F there are _________ protons, _________ neutrons, and __________ electrons

• 9, 9, 9
• 19, 19, 19
• 9, 10, 9
• 10, 9, 10

Tags

NGSS.MS-PS1-1

Nitrogen and hydrogen can each exist as two isotopes. This means that molecules of ammonia (NH₃) could exist having several different masses. How many different masses of ammonia molecules would be possible?

• 1 
• 2
• 4
• More than 4

Tags

NGSS.HS-PS1-7

A new element has two isotopes, one with a mass of 40.0amu and the other with a mass of 42.0amu. The atomic weight is 40.50amu. Pick the true statement.

• Both isotopes are equally abundant. 
• The isotope at 42.0 amu is more abundant.
•  The isotope at 40.0 amu is more abundant.
• Impossible to determine without percent abundances of each isotope.

A hypothetical element consists of 3 isotopes with the masses and natural abundances shown.  What is the average atomic mass?

• 39.9
• 40.1
• 39.2
• 40.9