37,38
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 see below

Explanation:

When multiplying or dividing, use the smallest number of significant figures (sf) of the digits provided.

37(a) 24 × 3.26 = 78.24      2 sf × 3 sf -->  round to 2 sf's

                          ≈ 78

   (b) 120 × 0.10 = 12            2 sf × 2 sf -->  round to 2 sf's

                          = 12

   (c) 1.23 × 2.0 = 2.46            3 sf × 2 sf -->  round to 2 sf's

                          = 2.5

    (d) 53 × 1.53 = 81.09            2 sf × 3 sf -->  round to 2 sf's

                          = 81

38(a)  4.84 ÷ 2.4 = 2.0167           3 sf × 2 sf -->  round to 2 sf's

                          = 2.0

   (b)  60.2 ÷ 20.1 = 2.995         3 sf × 3 sf -->  round to 3 sf's

                            = 3.00

    (c) 102.4 ÷ 51.2 = 2               4 sf × 3 sf -->  round to 3 sf's

                          = 2.00

    (d) 168 ÷ 58 = 2.896                  3 sf × 2 sf -->  round to 2 sf's

                          = 2.9

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

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