Question

directions: circle the letter in front of the word or words that best complete the statement.

1. elements on distant stars are identified

a. by examining their spectra with a telescope.
b. by examining their spectra with a microscope.
c. by testing and comparing samples from the stars with earth.
d. by comparing their spectra with known spectra here, on earth.

1. the sample was held in the flame with a

a. pair of tongs.
b. test tube.
c. crucible.
d. wire.

1. the flame test color for sodium is

a. red.
b. green.
c. yellow.
d. violet.

1. the flame test color for potassium is

a. red.
b. green.
c. yellow.
d. violet.

1. the cobalt glass is used to

a. eliminate the violet light.
b. eliminate the yellow light.
c. eliminate the green light.
d. eliminate the red light.

Explanation:

1. Elements on distant stars are identified by comparing their spectra with known spectra on Earth. Telescopes are for observing light from stars (not just spectra), microscopes are for small objects, and we can't get samples from most stars.
2. In a flame test, the sample is held in the flame with a wire. Tongs are too big, a test tube would melt, and a crucible is for heating solids in a furnace.
3. The flame test color for sodium is yellow.
4. The flame test color for potassium is violet (with a lilac hue).
5. Cobalt glass is used to eliminate the yellow light (usually from sodium impurities) so that the true color of other elements (like potassium) can be seen.

Answer:

1. d. by comparing their spectra with known spectra here, on Earth.
2. d. wire.
3. c. yellow.
4. d. violet.
5. b. eliminate the yellow light.