Y10 LC2 CHEM HWK #2 - % element and reacting masses

How many HCl molecules do you need to balance this equation? 
Mg +  __HCl --->  MgCl₂ + H₂

• 1
• 2
• 3
• 4

Tags

NGSS.MS-PS1-5

What is the percentage of sodium, Na, in sodium chloride, NaCl?

(Na = 23, Cl = 35.5)

• 39%

• 61%

• 35%

• 65%

Which compound has 42% of chlorine (Cl) in it?

percentage = (mass of element / Mr) x 100

• HClO (Mr = 52)

• HClO₂ (Mr = 68)

• HClO₃ (Mr = 84)

• HClO₄ (Mr = 100)

What is the correct % of each element in water, H₂0?

(H = 1, O = 16)

• H = 11.1%

  O = 89.9%

• H = 66.7%

  O = 33.3%

• H = 5.6%

  O = 89.9%

• H = 20%

  O = 80%

Which shows the correct % of each element in Cu₂S?

(Cu = 63.5, S = 32)

• %Cu= 67.987 %S= 32.013

• %Cu= 79.854 %S= 20.145

• %Cu= 35.946 %S= 64.054

Given the equation:

2NaClO₃ (s) → 2NaCl (s) + 3O₂ (g)

2.00 moles of NaClO₃ will produce how many grams of O₂?

(Mr of O₂ = 32)

• 56 g of O₂

• 96 g of O₂

• 64 g O₂

• 32 g O₂

Using the following equation:
Fe₂O₃(s) + 3H₂(g) → 2Fe(s) + 3H₂O(l)
How many moles of iron can be made from  6 moles H₂? 

• 4 moles Fe
• 6 moles Fe
• 9 moles Fe
• 2 moles Fe

Tags

NGSS.HS-PS1-7

2Na + 2H₂O → 2NaOH+ H₂

46 : 36 : 80 : 2

How many grams of hydrogen are produced if 120 g of Na are available?

• 5.21 g

• 2.6 g

• 690 g

• 45 g

• 60 g

2H₂ + O₂ −−〉 2H₂O

How many grams of H₂O can be produced from 3.91 g of O₂?

• 1.905

• 4.4

• 2.2

• 1.1

2Al + 3H₂SO₄ -> Al₂(SO₄)₃ + 3H₂

How many grams of aluminum sulfate would be formed if 250g H₂SO₄ completely reacted with aluminum?

(Al = 27, H = 1, S = 32, O=16)

• 0.85 g

• 290 g

• 450 g

• 870 g