1: which statement is true about sand and baking soda?

both are mixtures.
both are pure substances.
sand is a mixture and baking soda is a pure substance.
sand is a pure substance and baking soda is a mixture.

2: which statement is true about sodium chloride (nacl)?

it is a salt because it decreases the concentration of metallic ions.
it is an acid because it is formed by the reaction of a salt and an acid.
it is a salt because it is formed by the reaction of an acid and a base.
it is an acid because it increases the concentration of nonmetallic ions.

3: boron is to the immediate left of carbon in the same row in the periodic table. which of the following statements compares the radius and pull exerted by the protons of boron and carbon atoms?

boron has a smaller radius and the protons in carbon exert a greater pull.
boron has a larger radius and the protons in carbon exert a greater pull.
boron has a smaller radius and the protons in carbon exert less pull.
boron has a larger radius and the protons in carbon exert less pull.

4: it takes 1 minute for a certain amount of potassium bromide (kbr) to dissolve in 100 grams of water at 25 °c.

which of the following will most likely happen if the same sample of potassium bromide is dissolved in 100 grams of water at 100 °c?

the sample will dissolve in exactly 1 minute.
the sample will dissolve in less than 1 minute.
the collision between particles of the sample will decrease.
the collision between particles of the sample will remain constant.

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1) Answer is: Sand is a mixture and baking soda is a pure substance.

Pure substance is made of only one type of atom or only one type of molecule (in this example baking soda NaHCO₃), it has definite and constant composition with distinct chemical properties.

Sand is a heterogeneous mixture.

A heterogeneous mixture have compounds that remain separate in the sample. Heterogeneous mixture is not uniform in composition (in this mixture different sand and small pebbles), but proportions of its components (in this mixture particles of different colors and size) vary throughout the sample.

2) Answer is: It is a salt because it is formed by the reaction of an acid and a base.

Balanced chemical reaction of forming sodium chloride:

HCl + NaOH → NaCl + H₂O.

Sodim chloride (NaCl) is crystaline solid compound.

Sodium is a metal and form cation Na⁺ and chlorine is nonmetal and form anion Cl⁻.

3) Answer is: Boron has a larger radius and the protons in carbon exert a greater pull.

The atomic radius of a chemical element is a measure of the size of its atom.The

Boron (B) has atomic number 5, it has 5 protons.

The atomic radius decreases across the periods because an increasing number of protons, because greater attraction between the protons and electrons.

Carbon has atomic number 6, it has 6 protons, so it has greater pull to electrons.

Atomic radius of the boron is 87 pm and of the carbon is 67 pm.

4) Answer is: The sample will dissolve in less than 1 minute.

The amount of solute that can be dissolved in a solvent depends of chemical composition, temperature and pressure.

Increasing temperature will add energy to solution and increase molecular motion.

Increased molecular motion causes more solvent molecules (in this example potassium bromide) to contact solute molecules, resulting in more dissolving.

the tides are influenced by both the moon and the sun, it's easy to see that when the sun lines up with the moon and the earth, as during a new moon or full moon, the tidal effect is increased. these are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal. on the other hand, if the sun and the moon are 90 degrees apart in relation to an observer on earth as during the first quarter moon or third quarter moon, then high tides are not as high as they normally would be. this is because despite its greater distance, the sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the moon's pull. this phenomenon of lower high tides is called a neap tide. if you need more information on this topic visit moonconnection.com.

the answers are

c and c