Here’s a list of all the Chocolate Frog Card locations in Pottermore…

Under the cut…

Morgana Card - located in Chapter 6: Moment 2 - Journey to Hogwarts - on the seat.

Albus Dumbledore located in Chapter 6: Moment 2 - Journey to Hogwarts - in the trunk under the table of the compartment with the candy strewn about (thanks @smartieshorts). 

Circe Card - located in Chapter 8: Moment 1 - lying on the stairs, you have to zoom in to see it…

Paracelsus Card - located in Chapter 8: Moment 3 - beside the barrel outside Hagrid’s shack…

Salazar Slytherin Card - located in Chapter 9: Moment 2 - In the trophy case…

Hengist of Woodcroft - located in Chapter 10: Moment 3 - Behind the troll, next to the Jack-o-lantern…

Helga Hufflepuff - located in Chapter 13: The Hooded Figure Moment - just right of the hooded figure, closer to you in the viewing plane…

Rowena Ravenclaw - located in Chapter 15: Moment 1 - on the windowsill in the very back of the scene…

Godric Gryffindor - located in Chapter 17: Moment 3 - Next to Mcgonagall’s goblet…

Merlin - located in Chapter 12: The Library Moment - on the lower half of the fourth bookcase, when you zoom all the way in. It’s blue. (thanks @mihyeon and @smartieshorts).

Cliodna - located in Chapter 17: The Hospital Wing Moment - on the chair (thanks @pokemonstadium).

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If you guys have any questions about the directions or more details about the ones for which my memory fails me, feel free to ask/reply about it…