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.
