Which element donates hydrogen ions when dissolved in water?

answer:

a) pto₂ + 2h₂ ⟶ pt   +   2h₂o

b) 0.021 g

c) 0.010 mol; 0.18 g

step-by-step explanation:

a) balanced equation

we know we will need a balanced equation with masses and molar masses, so let’s gather all the information in one place.  

m_r:                 2.016   195.08   18.02

            pto₂ + 2h₂ ⟶ pt   +   2h₂o

m/g:                               1.0

b) mass of h₂

(i) calculate the moles of pt

n = 1.0 g pt   × (1 mol pt /195.08 g pt)

  = 5.13 × 10⁻³ mol pt

(ii) calculate the moles of h₂

the molar ratio is (2 mol h₂/1 mol pt)

n = 5.13 × 10⁻³ mol pt × (2 mol h₂/1 mol pt)

  = 0.0103 mol h₂

(iii) calculate the mass of h₂

m = 0.0103 mol h₂× (2.016 g h₂/1 mol h₂)

m = 0.021 g h₂

you need 0.021 g h₂ to produce 1.00 g pt.

c) moles of water

the molar ratio is (2 mol h₂o/1 mol pt)

  moles of h₂o = 5.13 × 10⁻³ mol pt × (2 mol h₂o/1 mol pt)

                        = 0.010 mol h₂o

mass of water = 0.010 mol h₂o × (18.02 g h₂o/1 mol h₂o)

                        = 0.18 g h₂o

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note: