chemistry alevel
5 A nitrate compound of a Group 2 metal, M, was thermally decomposed.
0.164 g of the metal nitrate gave 2.5 × 10−3 mol of gas.
The equation for the reaction is
2M(NO3)2(s) o 2MO(s) + 4NO2(g) + O2(g)
What is metal M?
A Magnesium
B Calcium
C Strontium
D Barium
hello why is the ans B i tried finding the mr for NO3 x2 and its 124 i tried addingit to any of the metals then divided mass by the mr to see which one gives the number of moles but i can't seem to get the ans can anyone help thanks !
0.164 g of the metal nitrate gave 2.5 × 10−3 mol of gas.
The equation for the reaction is
2M(NO3)2(s) o 2MO(s) + 4NO2(g) + O2(g)
What is metal M?
A Magnesium
B Calcium
C Strontium
D Barium
hello why is the ans B i tried finding the mr for NO3 x2 and its 124 i tried addingit to any of the metals then divided mass by the mr to see which one gives the number of moles but i can't seem to get the ans can anyone help thanks !
Original post by staerryynighht
5 A nitrate compound of a Group 2 metal, M, was thermally decomposed.
0.164 g of the metal nitrate gave 2.5 × 10−3 mol of gas.
The equation for the reaction is
2M(NO3)2(s) o 2MO(s) + 4NO2(g) + O2(g)
What is metal M?
A Magnesium
B Calcium
C Strontium
D Barium
hello why is the ans B i tried finding the mr for NO3 x2 and its 124 i tried addingit to any of the metals then divided mass by the mr to see which one gives the number of moles but i can't seem to get the ans can anyone help thanks !
0.164 g of the metal nitrate gave 2.5 × 10−3 mol of gas.
The equation for the reaction is
2M(NO3)2(s) o 2MO(s) + 4NO2(g) + O2(g)
What is metal M?
A Magnesium
B Calcium
C Strontium
D Barium
hello why is the ans B i tried finding the mr for NO3 x2 and its 124 i tried addingit to any of the metals then divided mass by the mr to see which one gives the number of moles but i can't seem to get the ans can anyone help thanks !
The moles in the question are the total moles of gas ie. on the right of the equation.......this isn’t the same as the moles of metal nitrate used.
Can you think how to use the equation given to find how many moles of the M nitrate are used.......(hint - think mole ratios) .....and then your original method should work out to give a match to one of the metals given.
Original post by cefox
The moles in the question are the total moles of gas ie. on the right of the equation.......this isn’t the same as the moles of metal nitrate used.
Can you think how to use the equation given to find how many moles of the M nitrate are used.......(hint - think mole ratios) .....and then your original method should work out to give a match to one of the metals given.
Can you think how to use the equation given to find how many moles of the M nitrate are used.......(hint - think mole ratios) .....and then your original method should work out to give a match to one of the metals given.
so i found number of moles of mno3 using mole ratio with the no2 gas then i took each mr to see which one will give us the same number of moles but it wont work !
Original post by staerryynighht
so i found number of moles of mno3
How many moles of metal nitrate do we have?
Let's simplify the equation a bit:
2 moles of metal nitrate -- > 5 moles of gas.
We have produced 2.5 x 10-3 moles of gas. Using ratios, this means 1 x 10-3 moles of metal nitrate have reacted (i.e. 2.5 x 10-3 x 2/5).
Mr = m / n = 0.164g / (1x10-3 moles) = 164.
Mr of metal + 124 (Mr of nitrate in compound) = 164. Therefore, Mr of metal = 164-124 = 40 i.e. the metal is Ca. Hope this helps!
2 moles of metal nitrate -- > 5 moles of gas.
We have produced 2.5 x 10-3 moles of gas. Using ratios, this means 1 x 10-3 moles of metal nitrate have reacted (i.e. 2.5 x 10-3 x 2/5).
Mr = m / n = 0.164g / (1x10-3 moles) = 164.
Mr of metal + 124 (Mr of nitrate in compound) = 164. Therefore, Mr of metal = 164-124 = 40 i.e. the metal is Ca. Hope this helps!
Original post by staerryynighht
so i found number of moles of mno3 using mole ratio with the no2 gas then i took each mr to see which one will give us the same number of moles but it wont work !
The O2 is a gas as well... so mole ratio is metal nitrate to gas = 1:5
Have just seen the answer given below for you....so take it from there
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