Hydrogen combines directly with

Options

A. `Ca`
B. `Cu`
C. `Zn`
D. `Fe`

Answer

To solve the question "Hydrogen combines directly with," we need to analyze the reactivity of the elements provided in the options. Here’s a step-by-step solution:

### Step 1: Understand the Question
The question asks which element can combine directly with hydrogen. This typically involves looking at the reactivity of the elements in the options provided.

**Hint:** Always start by identifying the key components of the question.

### Step 2: Recall the Reactivity Series
The reactivity series is a list of metals arranged in order of decreasing reactivity. The more reactive metals can displace less reactive metals from their compounds and can react directly with hydrogen.

**Hint:** Remember that in the reactivity series, the higher an element is, the more reactive it is.

### Step 3: Identify the Elements
Assuming the options given are common metals like Calcium (Ca), Copper (Cu), Zinc (Zn), and Iron (Fe), we need to place them in the reactivity series.

**Hint:** Familiarize yourself with the common reactivity series of metals.

### Step 4: Arrange the Elements in the Reactivity Series
From the reactivity series, we can arrange the elements as follows:
- Potassium (K)
- Sodium (Na)
- Calcium (Ca)
- Magnesium (Mg)
- Aluminum (Al)
- Zinc (Zn)
- Iron (Fe)
- Lead (Pb)
- Copper (Cu)
- Silver (Ag)
- Gold (Au)

Among the options, Calcium is the most reactive.

**Hint:** The higher the position in the series, the more likely it is to react with hydrogen.

### Step 5: Determine Which Element Combines with Hydrogen
Since Calcium is the most reactive among the options provided, it will readily combine with hydrogen to form calcium hydride (CaH₂).

**Hint:** Look for the element that is highest in the reactivity series among the options.

### Conclusion
Thus, the correct answer is Calcium (Ca), as it combines directly with hydrogen.

**Final Answer:** Calcium (Ca)

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