Calculate the number of moles of NaOH contained in 250. mL of a 0.05M solution.

0.0125mol

Explanation:

Molarity (M) = number of moles (n) ÷ volume (V)

n = Molarity × Volume

According to this question, a 0.05M solution contains 250 mL of NaOH. The volume in litres is as follows:

1000mL = 1L

250mL = 250/1000

= 0.250L

n = 0.05 × 0.250

n = 0.0125

The number of moles of NaOH is 0.0125mol.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g